Optical disc, optical disc manufacturing method, optical disc recording device and optical disc reproduction device

ABSTRACT

Sub-information necessary to reproduce main information is recorded without deteriorating the reading accuracy of the main information, so that the illegal duplication of an optical disc is prevented. An optical disc  1  is produced by forming a reflective film  1 L on concave and convex marks MK after the concave and convex marks MK synchronized with the integral multiple of a channel bit length are formed in accordance with modulated main information. Thereafter, continuous or intermittent laser light synchronized with the integral multiple of the channel bit length is irradiated at intervals longer than the longest one of the concave and convex marks MK in accordance with a spiral track formed in a circumferential direction of the concave and convex marks MK, whereby an optical characteristic of the reflective film  1 L is changed to form a recordable mark SMK and sub-information necessary to reproduce the main information is recorded in a superimposition manner.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an optical disc such as a CD, a DVD ora Blu-ray disc, an optical disc manufacturing method for manufacturingan optical disc, an optical disc recording device for recordinginformation on an optical disc and an optical disc reproduction devicefor reproducing information from an optical disc.

2. Description of the Background Art

Conventionally, optical discs are widely used as inexpensive recordingmedia for digital information. For example, a Blu-ray disc has acapacity of 25 gigabytes with a single layer and 50 gigabytes with twolayers and can record high-vision and good-quality video contents about2 to 4.5 hours. Accordingly, as the optical disc capacity increases, thevalue of digital contents recorded on one optical disc increases and theprotection of the copyright of the recorded digital content has becomean essential technical problem.

However, nowadays, there are a great number of illegal optical discmanufacturer such as pirate makers for illegally duplicating digitalcontents from optical discs. This hinders a sound distribution ofdigital copyrighted works and creates a situation where profits are notfairly distributed to copyright holders.

Accordingly, technology for changing the reflectivity of a reproductionfilm on concave and convex marks by laser irradiation used for trackingof a guide groove in an optical disc having a digital copyrighted workrecorded by the concave and convex marks is disclosed, for example, inpatent document 1.

By using the optical disc disclosed in patent document 1, optical discswhich need not be collected can be provided even if they are used, forexample, for rental.

Further, for example, patent document 2 discloses technology forrecording sub-information by locally changing the reflectivity of aninformation recording surface at a position at a specified distance fromthe edge of a mark or space based on a sub-data string for marks orspaces with a specified length or longer out of concave and convexmarks.

According to the invention disclosed in patent document 2, thereflectivity of the mark or space is locally changed at such a timing asnot to influence the positional information of the edge of the concaveand convex mark. This enables the recording of sub-information thatmakes illegal copying difficult without influencing reproduction of amain data string represented by a mark string by an optical pickup.

Further, for example, patent document 3 discloses an informationrecording/reproducing method by which, using a recording medium which isoptically changed depending on the quantity of irradiated laser light,laser light intensity modulated by a signal having the same band as afirst signal obtained by modulating a signal such as a video or a datasignal according to the quantity of laser light and having a recordingstate ON/OFF controlled by a second signal in a band lower than that ofthe first signal is irradiated twice or more to the same informationtrack on the recording medium having the first signal already recordedwith positions on the recording medium synchronized, the second signalis recorded in a superimposition manner to further optically change apart irradiated with the laser light, and the second signal is separatedand reproduced at the time of reproduction.

According to the invention disclosed in patent document 3, by recordingthe second signal on the same information track in a superimpositionmanner as information indicating the deletion of the information of thefirst signal or information indicating the position of an informationtrack as an alternative to the information of the first signal, themanagement of the information track on the recording medium can berealized without judging whether the information of the informationtrack is valid or invalid or providing a special information track formanaging the position of the information track as an alternative to theinformation track.

Further, for example, patent document 4 discloses an optical discincluding a spiral first information track having specified datarecorded thereon and a spiral second information track formed in aregion between track parts of the first information track and havingcopy detection information recorded thereon.

According to the invention disclosed in patent document 4, by recordingdetection information used for copy disc discrimination on the secondinformation track different form the first information track for data,an illegally copied disc can be effectively checked without influencinga normal operation. Further, by recording security information on thesecond information track, the illegal duplication of the securityinformation can be prevented.

However, by any of these methods, it is difficult to record mediumunique information of the optical disc while preventing the illegalduplication without increasing cost required for the manufacturing ofthe optical disc and without deteriorating the reading accuracy of maininformation. It is also difficult to record the medium uniqueinformation of the optical disc while efficiently preventing illegalduplication without sacrificing the recording region for the maininformation.

These are for the following reasons. In the invention disclosed inpatent document 1, the guide groove is formed on the optical discbeforehand in order to change the reflectivity of the irradiated part byirradiating a recording laser beam of a specified intensity or higher tothe optical disc. Normally, in the case of manufacturing an optical discformed with a guide groove and concave and convex marks, it is necessaryto record the guide groove to locate the concave and convex marks in thecenter after the concave and convex marks are recorded in an opticaldisc master or to record the concave and convex marks after the guidegroove is recorded. However, in the case of a Blu-ray disc, accuracy inthe order of several tens nanometers in a radial direction is necessaryfor positioning between these tracks, and it is difficult to record boththe guide groove and the concave and convex marks using a normalmastering apparatus. In order to realize this, a special masteringapparatus is necessary and an increase of cost required for themanufacturing of an optical disc is unavoidable.

In the invention disclosed in patent document 2, laser light isirradiated to a position at the specified distance from the edge of themark or space with the specified length or longer. Thus, it is necessaryto search and save the mark or space with the specified length orlonger, whereby a recording time for recording the sub-information isuselessly consumed and cost required for the manufacturing of theoptical disc increases. In the case of recording the sub-information,for example, only on a synchronization code known to have a mark orspace with the specified length or longer, a corresponding recordingregion is necessary to record the medium unique information of a hundredand several tens bytes. Therefore, in this case as well, the recordingtime or reproduction time is uselessly consumed.

In the invention disclosed in patent document 3, the second signal isrecorded on the part prerecorded with the first signal a plurality oftimes in a superimposition manner, and this recording is repeated untilthe second signal can be normally read. Accordingly, the readingaccuracy of the prerecorded first signal deteriorates and a recoverabledefect margin such as an error correction deteriorates.

In the invention disclosed in patent document 4, the second informationtrack having the security information recorded thereon is formed in thepartial region between the track parts of the first information trackand the first and second information tracks are arranged such that theposition of the second information track is reached upon a movement fromthe first information track by one track pitch. However, the formationof the second information track between the track parts of the firstinformation track means to double the track pitch of the adjacent partsof the first information track, wherefore the region for recording themain information is sacrificed by forming the second information track.In other words, recording capacity per optical disc is reduced byforming the second information track.

Patent document 1:

Japanese Unexamined Patent Publication No. H09-306030

Patent document 2:

Japanese Patent No. 3454410

Patent document 3:

Japanese Patent No. 2903422

Patent document 4:

Japanese Unexamined Patent Publication No. H08-147767

DISCLOSURE OF THE INVENTION

In view of the above problems, an object of the present invention is toprovide an optical disc, an optical disc manufacturing method, anoptical disc recording device and an optical disc reproduction devicecapable of recording sub-information necessary to reproduce maininformation without deteriorating the reading accuracy of the maininformation, so that the illegal duplication of optical discs isprevented.

An optical disc according to one aspect of the present invention isdirected to an optical disc in which a reflective film is formed onconcave and convex marks after the concave and convex marks synchronizedwith the integral multiple of a channel bit length are formed inaccordance with modulated main information, characterized in that, afterthe optical disc is produced, continuous or intermittent laser lightsynchronized with the integral multiple of the channel bit length isirradiated at intervals longer than the longest one of the concave andconvex marks in accordance with a spiral track formed in acircumferential direction of the concave and convex marks to change anoptical characteristic of the reflective film, thereby forming arecordable mark to record sub-information necessary to reproduce themain information in a superimposition manner.

Another aspect of the present invention is directed to an optical discmanufacturing method, comprising a mastering step of producing anoptical disc master formed with concave and convex marks synchronizedwith the integral multiple of a channel bit length in accordance withmodulated main information; a stamping step of transferring the concaveand convex marks of the optical disc master to an optical discsubstrate; a sputtering step of forming a reflective film on the opticaldisc substrate; and a sub-information recording step of irradiatingcontinuous or intermittent laser light synchronized with the integralmultiple of the channel bit length at intervals longer than the longestone of the concave and convex marks in accordance with a spiral trackformed in a circumferential direction of the concave and convex marks tochange an optical characteristic of the reflective film after thereflective film is formed on the concave and convex marks of the opticaldisc in the sputtering step, thereby forming a recordable mark to recordsub-information necessary to reproduce the main information in asuperimposition manner.

Still another aspect of the present invention is directed to an opticaldisc recording device for recording sub-information necessary toreproduce main information on an optical disc prerecorded with the maininformation by concave and convex marks, comprising a tracking unit forcontrolling a position to be irradiated with laser light in accordancewith a spiral track formed in a circumferential direction of the concaveand convex marks; a reproduction signal extracting unit for extracting areproduction signal from the reflected light of reproduction laser lightirradiated to the concave and convex marks; a clock extracting unit forextracting a channel clock synchronized with a channel bit length of theconcave and convex marks; and a sub-information recording unit forirradiating recording laser light synchronized with a band which is theintegral multiple of the channel clock and lower than the band of thereproduction signal to change an optical characteristic of a reflectivefilm formed on a recording surface of the optical disc, thereby forminga recordable mark to record the sub-information on the optical disc in asuperimposition manner.

Further another aspect of the present invention is directed to anoptical disc reproduction device for reproducing main information fromconcave and convex marks of an optical disc and reproducingsub-information necessary to reproduce the main information from arecordable mark formed by changing an optical characteristic of areflective film of the optical disc through the irradiation of laserlight, comprising a tracking unit for controlling a position to beirradiated with the laser light in accordance with a spiral track formedin a circumferential direction of the concave and convex marks; areproduction signal extracting unit for extracting a reproduction signalfrom the reflected light of reproduction laser light irradiated to theconcave and convex marks; a clock extracting unit for extracting achannel clock synchronized with a channel bit length from thereproduction signal; a separating unit for separating a concave andconvex mark reproduction signal corresponding to the concave and convexmarks and a recordable mark reproduction signal corresponding to therecordable mark from the reproduction signal; and a sub-informationreproducing unit for reproducing the sub-information from the recordablemark reproduction signal synchronized with a band which is the integralmultiple of the channel clock and lower than the band of the concave andconvex mark reproduction signal.

Still another aspect of the present invention is directed to an opticaldisc including a main information recording region where maininformation is recorded by concave and convex marks and asub-information recording region where sub-information necessary toreproduce the main information is recorded by a recordable mark formedby irradiating laser light after the concave and convex marks areformed, characterized in that the recordable mark is formed in thesub-information recording region by irradiating the laser light from arecording starting point based on an angular position of a referenceposition in the main information recording region to change thereflectivity of a reflective film, whereby the sub-information isrecorded in a superimposition manner.

Still another aspect of the present invention is directed to an opticaldisc recording device for recording main information and sub-informationon an optical disc including a main information recording region wheremain information is recorded by concave and convex marks and asub-information recording region where sub-information necessary toreproduce the main information is recorded by a recordable mark formedby irradiating laser light after the concave and convex marks areformed, comprising a clock generator for generating a clock signalsynchronized with the rotation of the optical disc; a reference angleextracting unit for extracting an angular position of a referenceposition in the main information recording region; and a sub-informationrecording unit for irradiating laser light synchronized with the clocksignal generated by the clock generator from a recording starting pointin the sub-information recording region specified based on the angularposition extracted by the reference angle extracting unit to record thesub-information in a superimposition manner.

Still another aspect of the present invention is directed to an opticaldisc reproduction device for reproducing main information andsub-information from an optical disc including a main informationrecording region where main information is recorded by concave andconvex marks and a sub-information recording region wheresub-information necessary to reproduce the main information is recordedby a recordable mark formed by irradiating laser light after the concaveand convex marks are formed, comprising a clock generator for generatinga clock signal synchronized with the rotation of the optical disc; areference angle extracting unit for extracting an angular position of areference position in the main information recording region; and asub-information reproducing unit for reproducing the sub-information insynchronism with the clock signal generated by the clock generator froma reproduction starting point in the sub-information recording regionspecified based on the angular position extracted by the reference angleextracting unit.

According to the present invention, the sub-information necessary toreproduce the main information can be recorded without deteriorating thereading accuracy of the main information, so that the illegalduplication of the optical disc can be prevented.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a conceptual diagram showing the construction of an opticaldisc according to a first embodiment,

FIG. 2 is a conceptual diagram showing a recording surface of a controlregion at an inner circumferential side of the optical disc according tothe first embodiment,

FIG. 3 is a conceptual diagram showing the recording surface of thecontrol region at the inner circumferential side of the optical discaccording to the first embodiment,

FIG. 4 is a conceptual diagram showing the recording surface of thecontrol region at the inner circumferential side of the optical discaccording to the first embodiment,

FIG. 5 is a diagram showing an optical disc manufacturing methodaccording to the first embodiment,

FIG. 6 is a block diagram showing the construction of an optical discrecording device according to the first embodiment,

FIG. 7 is a timing chart showing a characteristic operation of theoptical disc recording device according to the first embodiment,

FIG. 8 is a block diagram showing the construction of an optical discreproduction device according to the first embodiment,

FIG. 9 is a timing chart showing a characteristic operation of theoptical disc reproduction device according to the first embodiment,

FIG. 10 is a conceptual diagram showing the construction of an opticaldisc according to a second embodiment,

FIG. 11 is a diagram showing an optical disc manufacturing methodaccording to the second embodiment,

FIG. 12 is a diagram showing a data format of physical positioninformation according to the second embodiment,

FIG. 13 is a block diagram showing the construction of a premarkrecording device according to the second embodiment,

FIG. 14 is a block diagram showing the construction of a physicalposition information acquiring apparatus according to the secondembodiment,

FIG. 15 is a timing chart showing a characteristic operation of thephysical position information acquiring apparatus according to thesecond embodiment,

FIG. 16 is a block diagram showing the construction of an optical discreproduction device according to the second embodiment,

FIG. 17 is a first flow chart showing an illegal disc judgment processin the optical disc reproduction device according to the secondembodiment,

FIG. 18 is a second flow chart showing the illegal disc judgment processin the optical disc reproduction device according to the secondembodiment,

FIG. 19 is a conceptual diagram showing the construction of an opticaldisc according to a third embodiment,

FIG. 20 is a block diagram showing the construction of an optical discrecording device according to the third embodiment,

FIG. 21 is a timing chart showing a characteristic operation of theoptical disc recording device according to the third embodiment,

FIG. 22 is a block diagram showing the construction of an optical discreproduction device according to the third embodiment,

FIG. 23 is a timing chart showing a characteristic operation of theoptical disc reproduction device according to the third embodiment,

FIG. 24A is a diagram showing recordable marks intermittently formedbetween tracks,

FIG. 24B is a diagram showing a recordable mark meandering on concaveand convex marks,

FIG. 24C is a diagram showing recordable marks having a short intervalin a circumferential direction and intermittently formed,

FIG. 24D is a diagram showing a recordable mark longer than the lengthof concave and convex marks in a radial direction and continuouslyformed, and

FIG. 24E is a diagram showing recordable marks longer than the length ofconcave and convex marks in a radial direction and intermittentlyformed.

BEST MODES FOR EMBODYING THE INVENTION

Hereinafter, embodiments of the present invention are described withreference to the accompanying drawings. The present invention can beembodied while being suitably changed without changing the essentialpoint thereof.

First Embodiment (1-1) Optical Disc According to First Embodiment

FIG. 1 is a conceptual diagram showing the construction of an opticaldisc 1 according to a first embodiment. The optical disc 1 shown in FIG.1 is comprised of a clamp region CLP, control regions CTL at inner andouter circumferential sides, and a user region USR.

The clamp region CLP is a feed portion upon loading the optical disc 1and, normally, no information is recorded thereon.

The control regions CTL are provided at two positions, i.e. at the innerand outer circumferential sides of the user region USR, and managementinformation, copyright information, physical characteristic informationor the like of the optical disc 1 is recorded by concave and convexrecording marks. The characteristic of the optical disc 1 is that amedium ID (medium unique information) is recorded by locally changingthe reflectivity of a reflective film 1L on the concave and convex markson the same track as the one formed by the concave and convex marks inthe control region CTL at the inner circumferential side through theirradiation of laser light. The medium ID is information for identifyingthe optical disc.

The optical disc 1 is formed by transferring concave and convex marks toan optical disc substrate 1P using a stamper, depositing (sputtering) areflective film 1L, whose reflectivity changes according to laserirradiation, on the concave and convex marks and covering the reflectivefilm 1L with a cover layer 1C, for example, by the application of a thinfilm sheet or by a spin coating method. After the optical disc 1 isproduced, the medium ID is recorded as information unique to eachoptical disc in a superimposition manner by laser irradiation to theconcave and convex marks in the control region CTL at the innercircumferential surface.

The reflective film 1L of the optical disc 1 may be realized by using apigmented film made of an organic material whose reflectivityirreversibly changes by the irradiation of laser light or by using aphase-change film such as a film made of an inorganic alloy material ora Te—O—Pd recording film. Information can be recorded on all of theserecording films by changing the reflectivities thereof through thermalfluctuation caused by the irradiation of laser light with a specifiedintensity.

FIGS. 2 to 4 are conceptual diagrams showing a recording surface of thecontrol region CTL at the inner circumferential side of the optical disc1 according to the first embodiment.

As described above, the optical disc 1 according to the first embodimentis formed by transferring concave and convex marks MK to the opticaldisc substrate 1P, for example, made of polycarbonate, depositing thereflective film 1L whose reflectivity changes through laser irradiationon the concave and convex marks, and recording reproducible managementinformation, copyright information, physical characteristic informationor the like as main information on the control region CTL at the innercircumferential side by laser irradiation.

After these pieces of main information are transferred to produce theoptical disc, recordable marks SMK are formed on the optical disc 1 bylocally changing the reflectivity of the reflective film 1L through theirradiation of laser light and the medium ID is recorded assub-information in a superimposition manner.

The feature of the recordable marks SMK shown in FIG. 2 is that therecordable marks SMK are formed by irradiating the laser light on thetracks formed by the concave and convex marks MK. Further, the width ofthe recordable marks SMK in a radial direction of the optical disc isnarrower than that of the concave and convex marks MK in the radialdirection of the optical disc. Thus, the fluctuation of the reflectedlight level caused by forming the recordable marks SMK can be madesmaller than the modulation factor of the concave and convex marks MK atthe time of reproduction, wherefore the deterioration of thereproduction accuracy of the concave and convex marks MK can be reduced.

By averagely setting the modulation factor of the recordable marks SMK,which is the fluctuation of the reflected light level produced byforming the recordable marks SMK, smaller than half the modulationfactor of the concave and convex marks MK as a difference between thereflected light level of the concave and convex marks MK and that of thereflective film other than the concave and convex marks MK, there is nolikelihood of erroneously reproducing the edge position of areproduction signal of the concave and convex marks MK. Therefore, thereproduction accuracy of the concave and convex marks MK is notinfluenced.

The recording band of the recordable marks SMK is lower than that of thelongest mark of concave and convex mark MK. Thus, it becomes possible toseparate the concave and convex marks MK and the recordable marks SMK bya band-limiting circuit (filter) at the time of reproduction, whereforemutual reproduction accuracies can be ensured.

The feature of the recordable marks shown in FIG. 3 is that therecordable marks SMK are formed by irradiating laser light on the tracksformed by the concave and convex marks MK. Further, the recordable marksSMK are discretely formed in a band lower than the recording band of thelongest one of the concave and convex marks MK. The width of onerecordable mark SMK discretely formed in a track direction is smallerthan that of the shortest one of the concave and convex marks MK andshorter than a channel bit length for recording the concave and convexmarks MK. Thus, the recordable marks SMK have a higher recording bandthan the concave and convex marks MK from a micro perspective whilehaving a lower recording band than the concave and convex marks MK froma macro perspective. Accordingly, it becomes possible to separate theconcave and convex marks MK and the recordable marks SMK by aband-limiting circuit (filter) at the time of reproduction, whereforemutual reproduction accuracies can be ensured.

Since the recordable marks SMK shown in FIG. 3 are discretely formed,the fluctuation amount of the reflected light level can be set smallerthan the fluctuation amount of the reflected light level of therecordable mark SMK shown in FIG. 2, whereby the influence on thereproduction accuracy of the concave and convex marks MK can be furtherreduced. On the other hand, the reproduction accuracy of the recordablemarks SMK shown in FIG. 3 is inferior to that of the recordable mark SMKshown in FIG. 2.

The feature of the recordable marks SMK shown in FIG. 4 is that therecordable marks SMK are formed by changing the reflectivity of thereflective film 1L between the tracks of the concave and convex marks MKthrough laser irradiation. Similar to the recordable marks SMK shown inFIGS. 2 and 3, those shown in FIG. 4 are recorded in a recording bandlower than that of the longest one of the concave and convex marks MK.Thus, the recordable marks SMK shown in FIG. 4 are better than thoseshown in FIGS. 2 and 3 in not influencing the reproduction accuracy ofthe concave and convex marks MK. On the other hand, at the time ofrecording, the recordable marks SMK shown in FIG. 4 is inferior to thoseshown in FIGS. 2 and 3 in needing an additional construction fortracking control between the tracks.

By the recordable marks SMK shown in FIGS. 2 to 4, identificationinformation unique to each medium can be recorded on the producedoptical disc 1 while reducing the influence on the reproduction accuracyof the concave and convex marks MK.

The optical disc 1 of the first embodiment preferably uses thereflective film 1L whose reflectivity increases by the irradiation oflaser light. This is because the reflectivity of a reflective film madeof a metal film in a normal read-only optical disc is reduced by theirradiation of laser light. Thus, if the reflectivity of the opticaldisc is increased by the irradiation of laser light, an effect ofpreventing illegal duplication is improved. Such a reflective film canbe realized by using an organic pigmented film or a phase-change film orby being initialized to have the above characteristic using aphase-change film.

(1-2) Optical Disc Manufacturing Method According to First Embodiment

FIG. 5 is a diagram showing an optical disc manufacturing methodaccording to the first embodiment. The optical disc manufacturing methodaccording to the first embodiment includes an authoring process 100, afirst manufacturing process 200, a second manufacturing process 300 anda checking process 400.

In the authoring process 100, content data to be recorded on the opticaldisc is authored in a disc format after being encrypted using anencryption key (master key) generated by a key management mechanism. Theauthored content data is outputted to the first manufacturing process200.

In the first manufacturing process 200, an input step 201, a masteringstep 202, a stamping step 203, a sputtering step 204 and a protectivefilm applying step 205 are successively performed in this order toproduce an optical disc having no medium ID recorded thereon.

In the input step 201, the content data generated in the authoringprocess 100 is inputted.

In the mastering step 202, a glass master having a photoresist appliedthereto is exposed with a laser or electron beam for development basedon the authored content data inputted from the authoring process 100,whereby a disc master cut with concave and convex marks is produced.

The disc master produced in the mastering step 202 has, thereafter,plating applied to a recording surface side where the concave and convexmarks are formed, thereby producing a stamper. The stamping step 203 isa so-called replication step of replicating this stamper, wherein anoptical disc substrate 1P having the concave and convex markstransferred by the injection molding of transparent resin is produced.

In the sputtering step 204, a reflective film is formed by sputtering ordeposition on the concave and convex marks of the optical disc masterhaving the concave and convex marks transferred thereto and produced inthe stamping step 203. This reflective film may be a pigmented film or aphase change film made of an inorganic alloy material or Te—O—Pdrecording film. In other words, these reflective films are those, thereflectivities of the recording films of which changes by theirradiation of laser light having a specified intensity and on whichirreversible recording marks can be formed. The optical discmanufacturing method of this embodiment is characterized by this pointas compared with normal optical disc manufacturing methods.

In the protective film applying step 205, a protective film 1C is formedon the concave and convex marks by applying a thin protective sheet orforming a thin film by spin coating on the optical disc substrate 1Phaving the reflective film applied in the sputtering step 204.

By the first manufacturing process 200 comprised of the above steps 201to 205, the optical disc having the concave and convex marks formed andhaving the reflective film with the changeable reflectivity by theirradiation of laser light formed on the concave and convex marks ismanufactured, and the second manufacturing process 300 follows.

In the second manufacturing process 300, a medium ID assigned with adigital certificate issued from the key management mechanism or anauthentication code such as a message authentication code (MAC) isrecorded on the optical disc manufactured in the first manufacturingprocess 200 by an optical disc recording device (sub-informationrecording device) 6.

The optical disc recording device 6 records the medium ID by reproducingthe concave and convex marks of the optical disc and changing thereflectivity of the reflective film on the concave and convex marksthrough the irradiation of laser light having recording intensity at aspecified timing based on the addresses of the concave and convex marks.The construction of the optical disc recording device 6 is described indetail in “(3-1) Optical Disc Recording Device According to FirstEmbodiment”. In this process, the medium ID is recorded on the opticaldisc, and the next checking process 400 follows.

In the checking process 400, whether or not the medium ID was normallyrecorded in the second manufacturing process 300 is checked by anoptical disc reproduction device 7. The optical disc reproduction device7 may be realized using the same device as the optical disc recordingdevice 6 in the second manufacturing process 300 or using a devicedifferent therefrom.

The optical disc reproduction device 7 reproduces the concave and convexmarks of the optical disc, generates a correlation sequence from aspecified timing based on the addresses of the concave and convex marks,and detects the medium ID by performing a correlation integral of areproduction signal obtained from the reflected light of the irradiatedlaser light and the correlation sequence. A method for judging whetheror not the medium ID was normally recorded in the checking process 400may be such that an error correction is performed using parity bitsassigned to the medium ID beforehand and judgment is made based on theerror bit number or such that the correlation integral is performedwithin a specified time, a resulting correlation integration value isjudged using a predetermined threshold value and the medium ID is judgedto be normal if the correlation integration value higher than thethreshold value is detected. The construction of the optical discreproduction device 7 is described in detail later in “(1-4) OpticalDisc Reproduction Device According to First Embodiment”.

Finally, in this checking process 400, an optical disc 5 having themedium ID normally recorded thereon is shipped as a final product.

As described above, if the optical disc manufacturing method of thefirst embodiment is used, the medium ID unique to each optical disc canbe additionally recorded even for the read-only optical discmanufactured by the input process, the mastering process, the stampingprocess, the sputtering process and the protective film applyingprocess. Further, since the second manufacturing process for recordingthe medium ID on the optical disc and the checking process 400 forchecking the presence of the medium ID recorded on the optical disc canbe realized by devices whose constituent elements are not largelydifferent from normal optical disc recording devices and optical discreproduction devices, there is no likelihood of increasing theproduction cost of the optical disc. Further, the medium ID is extractedby detecting a fine fluctuation of the reflected light at the time ofreproducing the concave and convex marks, specifically extracted byperforming a correlation integral of the reproduction signal of theconcave and convex marks and the correlation sequence secretly producedinside. Thus, the manufacturing of the optical disc by pirate makers whocannot know the medium ID and the duplication thereof can be prevented.Further, since the recordable marks recording the medium ID are recordedby changing the reflectivity through the irradiation of laser light,there is sufficient resistance to illegal duplication methods fortransferring information by peeling off the protective film 1C.

(1-3) Optical Disc Recording Device According to First Embodiment

FIG. 6 is a block diagram showing the construction of the optical discrecording device used in the second manufacturing process of the opticaldisc manufacturing method according to the first embodiment. The opticaldisc recording device 6 records the medium ID assigned with theauthentication code by the key management mechanism in a superimpositionmanner on the optical disc having the reflective film whose reflectivitychanges through the irradiation of laser light applied on the concaveand convex marks after the optical disc is produced in the firstmanufacturing process 200.

The optical disc recording device 6 shown in FIG. 6 is provided with amemory 11, a spindle motor 12, an optical head 13, a servo circuit 14,an analog signal processor 15, a digital signal processor 16, aformatter 17, a timing generator 18, a random number generator 19, anEOR 20, a PE modulator 21, a laser intensity modulator 22 and a systemcontroller 23.

The memory 11 is for saving the medium ID received from the keymanagement mechanism beforehand. The medium ID is normally informationupdated medium by medium so as to be unique to each medium.

The spindle motor 12 rotates an optical disc 241 at a rotation speedcorresponding to the optical disc 241 when the optical disc 241 formedin the first manufacturing process 200 and having no medium ID recordedthereon is inserted into a drive.

The optical head 13 irradiates the optical disc 241 with laser lighthaving reproduction intensity when the rotation speed of the opticaldisc 241 reaches a target rotation speed, generates a channel signal CSfrom the reflected light and outputs it to the analog signal processor15.

The analog signal processor 15 generates a focus error signal FEindicating a displacement of a focus position and a tracking errorsignal TE indicating a displacement of a tracking position with respectto the concave and convex marks in accordance with the channel signal CSinputted from the optical head 13, and outputs them to the servo circuit14. The analog signal processor 15 also generates an analog reproductionsignal AS corresponding to the concave and convex marks by equalizingthe waveforms of the channel signal CS inputted from the optical head 13or amplifying the channel signal CS, and outputs it the digital signalprocessor 16.

The servo circuit 14 generates a focus control signal FC and a trackingcontrol signal TC for controlling the focus position and the trackingposition of a spot position of the laser light in accordance with thetracking error signal TE and the focus error signal FE inputted from theanalog signal processor 15, and outputs them to the optical head 13. Theoptical head 13 finely adjusts the focus position and the trackingposition in accordance with these control signals. Further, the servocircuit 14 generates a rotation control signal SC for finely adjustingthe rotation speed based on a radial position, and outputs it to thespindle motor 12. The spindle motor 12 finely adjusts the rotation speedin accordance with the rotation control signal SC inputted from theservo circuit 14.

The digital signal processor 16 extracts binary digital reproductiondata from the analog reproduction signal AS inputted from the analogsignal processor 15. The digital signal processor 16 is internallyprovided with a PLL (Phase Locked Loop) circuit, extracts asynchronizing clock signal CK in accordance with the analog reproductionsignal AS inputted from the analog signal processor 15, samples theanalog reproduction signal AS using the extracted clock signal CK toquantize it, then generates a digital reproduction signal DS bybinarizing the quantized analog reproduction signal AS and outputs it tothe formatter 17. The digital signal processor 16 outputs the extractedclock signal CK to the timing generator 18.

The formatter 17 detects synchronization codes assigned at specifiedtime intervals from the digital reproduction signal DS inputted from thedigital signal processor 16, formats it into a frame structure, dividesit into sector units (address units) including a plurality of frames andhaving address information to reproduce address information ADR, andoutputs the address information ADR to the timing generator 18 and therandom number generator 19. The formatter 17 also outputs asynchronization code detection timing signal SY indicating a detectiontiming of the synchronization code to the timing generator 18.

The timing generator 18 generates a timing of recording the medium IDfrom the address information ADR inputted in synchronism with the clocksignal CK inputted from the digital signal processor 16. The timing isthat of a sub-frame indicating an interval for recording one bit of themedium ID and is generated by a counter synchronized with the clocksignal CK and the synchronization code detection timing signal SY. Asub-frame count value CNT indicating a sub-frame position generated bythe counter is outputted to the random number generator 19 and thememory 11. The timing generator 18 generates a PE modulation signal PEfor applying a PE modulation to the medium ID to be recorded tosubstantially equalize a displacement probability of the recordablemarks toward the outer circumferential side and that of the recordablemarks toward the inner circumferential side using a similar counter, andoutputs it to the PE modulator 21. The timing generator 18 alsogenerates an initial value set timing signal SET as a timing ofpresetting an initial value to a random sequence and outputs it to therandom number generator 19.

The random number generator 19 presets the address information ADR fromthe formatter 17 as an initial value at an output timing of the initialvalue set timing signal SET inputted from the timing generator 18.Further, the random number generator 19 generates a pseudo randomsequence RN bit by bit at the increment timing of the sub-frame countvalue CNT inputted from the timing generator 18 and outputs it to theEOR 20. Although the address information ADR is used as an initial valuein this embodiment, the present invention is not limited to this. If theaddress information ADR is data converted by a one-way function or thelike, resistance to the illegal recording of the medium ID can befurther improved since pirate makers, who do not know this method,cannot generate a similar random number sequence. Further, the initialvalue may have a secret inside or may be recorded as a concave andconvex mark on the medium. The random number generator 19 is a generalM-sequence generator including a shift register, and generates thepseudo random sequence bit by bit by shifting the internal shiftregister at every increment timing of the sub-frame count value.

The memory 11 extracts the bit corresponding to the count value from themedium ID received from the key management mechanism and storedbeforehand based on the sub-frame count value CNT from the timinggenerator 18, and outputs it as sub-information SD to the EOR 20.

The EOR 20 is constructed by a general XOR gate, calculates an exclusiveOR of one bit of the pseudo random sequence RN inputted from the randomnumber generator 19 and one bit of the medium ID inputted from thememory 11 to generate diffuse sub-information RSD and outputs it to thePE modulator 21.

Similar to the EOR 20, the PE modulator 21 is also constructed by ageneral XOR gate, applies a PE modulation to the diffuse sub-informationRSD by calculating an exclusive OR of the diffuse sub-information RSDinputted from the EOR 20 and the PE modulation signal PE inputted fromthe timing generator 18, thereby generating post-PE modulation diffusesub-information PRSD, and outputs it to the laser intensity modulator22.

The laser intensity modulator 22 increases a current flowing into alaser in a section “H” of the post-PE modulation diffuse sub-informationPRSD inputted from the PE modulator 21, thereby modulating laser lightwith recording intensity into a recording pulse WP for irradiation, andoutputs the recording pulse WP to the optical head 13. This laserirradiation intensity modulation may be in the form of multiple pulsesfor increasing and decreasing the laser intensity at high speed or maybe in the form of irradiation of laser light with specified intensityhigher than the reproduction intensity. Which laser irradiation methodis adopted does not matter at least if the reflectivity of thereflective film changes by the irradiation of laser light.

The optical head 13 controls the amount of the current flowing into thelaser using the recording pulse WP from the laser intensity modulator 22while executing a tracking control to the track of the concave andconvex marks by the servo circuit 14, whereby the reflective film of theoptical disc 241 is irradiated with the laser light whose intensity wasadjusted and the medium ID is recorded in a superimposition manner byforming the recordable marks, whose reflectivity was changed, on theconcave and convex marks.

In this embodiment, the spindle motor 12, the optical head 13, the servocircuit 14 and the analog signal processor 15 correspond to an exampleof a tracking unit, the analog signal processor 15 to an example of areproduction signal extracting unit, the digital signal processor 16 toan example of a clock extracting unit, and the memory 11, the opticalhead 13, the formatter 17, the timing generator 18, the random numbergenerator 19, the EOR 20, the PE modulator 21 and the laser intensitymodulator 22 to an example of a sub-information recording unit.

Next, the operation of the optical disc recording device 6 is describedin detail with respect to an exemplary case where the optical disc ofthis embodiment is a Blu-ray ROM disc. FIG. 7 is a timing chart showinga characteristic operation of the optical disc recording deviceaccording to the first embodiment.

Physical clusters as units for performing one error correction (64kilobytes in user data) are consecutively recorded on a track in theBlu-ray ROM disc. Each physical cluster is made up of 16 address unitseach having address information ADR. Each address unit is made up of 31frames each having a synchronization code. Further, one frame is made upof 1932 channel bits.

Accordingly, the formatter 17 of the optical disc recording device 6formats the digital reproduction signal DS from a digital lead channelinto a frame structure by detecting the synchronization codes therefromand divides it into address units as recording units of the addressinformation ADR while judging which frame in the address unit by thepattern of the synchronization codes.

The timing generator 18 of the optical disc recording device 6 countsthe sub-frames for recording one bit of medium information by countingone frame as “+1” in the units of 138 channel bits, generates thesub-frame count value CNT and outputs it to the random number generator19 and the memory 11. Further, the timing generator 18 generates such aPE modulation signal PE that first 69 channel bits are “L” and thefollowing 69 channel bits are “H” although not shown as a signal, andoutputs it to the PE modulator 21.

The memory 11 extracts the medium ID stored beforehand bit by bit assub-information SD corresponding to the sub-frame count value CNT at thetiming of incrementing the sub-frame count value CNT inputted from thetiming generator 18, and outputs it to the EOR 20.

The random number generator 19 generates the pseudo random sequence RNbit by bit at the timing of incrementing the similarly inputtedsub-frame count value CNT and outputs it to the EOR 20. In thisembodiment, a target address where the recording of the medium ID isstarted is described to be “N”. Thus, the initial value set timingsignal SET for setting the initial value of the random number generator19 is outputted before the starting end of the address unit of anaddress N from the timing generator 18, and the initial value is set inthe M-sequence generating shift register of the random number generator19. Address data converted beforehand by a one-way function or theinitial value secretly stored inside may be used as this initial valueas described above. In Blu-ray, addresses are not actually recorded atthe leading ends of the address units, but are recorded in discreteareas in the address units called BIS clusters. Thus, the address tocome is not determined at the leading end of the address unit.Accordingly, the address is extracted from the address unit immediatelybefore the address unit of the target address where the recordable markis recorded, and an address obtained by adding “+2” to the extractedaddress is used as an initial value of the random number generator 19(since the address is incremented by “+2” for each address unit inBlu-ray discs).

The EOR 20 calculates an exclusive OR of the pseudo random sequence RNinputted from the random number generator 19 and each bit in thesub-frame of the sub-information SD to generate the diffusesub-information RSD, and outputs it to the PE modulator 21.

The PE modulator 21 applies a PE modulation to the diffusesub-information RSD by calculating an exclusive OR of the inputted PEmodulation signal PE and the diffuse sub-information RSD, therebygenerating the post-PE modulation diffuse sub-information PRSD, andoutputs it to the laser intensity modulator 22.

The laser intensity modulator 22 irradiates laser light havingreproduction intensity in an “L” section of the post-PE modulationdiffuse sub-information PRSD inputted from the PE modulator 21 andirradiates laser light having recording intensity in an “H” section. Thelaser intensity modulator 22 forms the recordable mark by irradiatingrecording laser light at an “H” timing of the post-PE modulation diffusesub-information PRSD to change the reflectivity of the reflective film.

As described above, the optical disc recording device 6 records themedium ID in a superimposition manner by irradiating the laser lightonto the track of the concave and convex marks MK formed by replicationto form the recordable marks. Thus, the optical disc recorded with themedium ID can be manufactured by forming the recordable marks on thetrack of the concave and convex marks having no medium ID recordedthereon.

In the case of forming the recordable marks longer than the maximum marklength of the concave and convex marks on the concave and convex marksas in this embodiment, it is necessary to make the fluctuation of thereflected light level caused by the recording of the recordable markssmaller than the modulation factor of the concave and convex marks atthe time of reproduction in order to avoid the influence on thereproduction accuracy of the concave and convex marks. This can berealized by making the width of the recordable marks smaller than theconcave and convex marks in the radial direction. Generally, it is knownthat the recording mark width monotonously increases according to laserintensity in a region where laser light of specified intensity isirradiated. Thus, the formation of the recordable marks narrower thanthe concave and convex marks can be realized by decreasing the laserintensity. The laser intensity can be regulated by regulating a timeduring which irradiation is made with high output power or by regulatingthe intensity of the power itself through the control of the value ofthe current flowing into the laser.

Next, the operation of the optical disc recording device 6 when therecordable mark recorded by changing the reflectivity through theirradiation of laser light is formed between the tracks formed by theconcave and convex marks as shown in FIG. 4 or 7 is supplementarilydescribed.

In this case as well, similar to the above, if the target address wherethe recordable mark is formed is “N”, the formatter 17 generates a trackjump signal TJ at the leading end position of the address unit havingthe address “N” and outputs it to the servo circuit 14 and the digitalsignal processor 16 as an additional operation of the optical discrecording device of FIG. 6.

The servo circuit 14 shifts the tracking position by half the track inaccordance with the track jump single TJ inputted from the formatter 17.A tracking control method of the servo circuit 14 at this time isdesirably a push-pull method for controlling the tracking position withrespect to the reflected light of the laser spot such that a differencebetween brightness at the inner circumferential side of the disc andbrightness at the outer circumferential side is “0”. This is because thetracking control can be stably executed even if no concave and convexmark is located in the center of the spot since the control is executedbased on the brightness difference between the inner circumferentialside and the outer circumferential side according to the push-pullmethod. In other words, the tracking control can be stably executedbetween the tracks having no concave and convex mark in the middle.Further, according to the push-pull method, the brightness differencebetween the inner circumferential side and the outer circumferentialside and a relationship of actually controlling the spot position at theinner circumferential side/outer circumferential side are reversed whenthe tracking control is executed between the tracks of the concave andconvex marks and when the control is executed in the track centers.Therefore, the control is executed while reversing the polarity of thepush-pull control at the time of a track jump.

The digital signal processor 16 fixes an oscillation frequency of theinternally provided PLL circuit in a region where the recordable mark isrecorded from the timing of the track jump signal TJ inputted from theformatter 17 and holds a clock frequency to be outputted. Normally, whenthe tracking control is executed between the tracks, there are problemsthat no stable reproduction signal of the concave and convex marks canbe obtained, the oscillation of the PLL circuit cannot be fixed, and therecordable mark cannot be formed at an intended position. However, theseproblems can be solved by fixing the clock frequency.

Normally, even if the oscillation frequency of the PLL circuit islocked, there is a problem that the concave and convex marks and theclock get out of synchronization and the formation position of therecordable mark is displaced if the recording time is long. Thus, therecordable mark is formed, for example, of a plurality of physicalclusters or a plurality of address units, and the frequency of the PLLcircuit is caused to follow the frequency of the concave and convexmarks immediately before the target address every time the recordablemark is formed. Thus, the recordable mark can be stably formed althoughthe recording time is increased more or less.

The servo circuit 14 controls the track position between the tracks atthe leading end position of the address unit having the target addresswhere the recordable mark is to be formed. Thereafter, the PE modulator21 applies a PE modulation to the diffuse sub-information RSD obtainedby scrambling the sub-information SD by the pseudo random sequence RNgenerated by the random number generator 19. The laser intensitymodulator 22 irradiates the optical disc with the laser light aftermodulating the intensity of the laser light based on the post-PEmodulation diffuse sub-information PRSD, and forms the recordable markbetween the tracks formed by the concave and convex marks. In this way,the medium ID can be recorded between the tracks.

In this way, the recordable mark can be formed between the tracks of theconcave and convex marks and the medium ID can be recorded withoutinfluencing the reproduction accuracy of the concave and convex marks atall.

Normally, in the case of forming the recordable marks, whosereflectivity was changed, between the tracks, a direct-current componentmay be included in a tracking error signal when the tracking iscontrolled to the concave and convex marks at the time of reproductionand the tracking operation may not be normally performed. However, sincethe recording pulse is used to apply the PE modulation to the recordablemark to be formed between the tracks in this embodiment, the areas wherethe recordable mark is formed and those where the recordable mark is notformed exist at a probability of 50%. Since the reflectivity between thetracks is constantly an average of the reflectivity of the recordablemarks and that of the reflective film other than the recordable marks ina band where the tracking control is executed, no extra direct-currentcomponent is outputted.

Next, the recording operation of the optical disc recording device 6when the medium ID is recorded by intermittently forming the recordablemarks on the track of the concave and convex marks through theirradiation of laser light as shown in FIG. 3 or 7 is supplementarilydescribed.

In this case, similar to the above, if the target address where therecordable mark is formed is “N”, the timing generator 18 generates onerecording gate signal WG for three channel bits from the above sub-framecounter for counting “+1” in the units of 138 channel bits in an area offorming the recordable mark from the leading end position of the addressunit having an address “N”, and outputs it to the laser intensitymodulator 22. The recording gate signal WG can be generated if beingoutputted at a timing where the remainder of the quotient obtained bydividing the count value of the sub-frame counter by 3 is “0”.

The PE modulator 21 applies a PE modulation to the diffusesub-information RSD obtained by scrambling the sub-information SD by thepseudo random sequence RN generated by the random number generator 19and outputs the post-PE modulation diffuse sub-information PRSD to thelaser intensity modulator 22. The laser intensity modulator 22 generatesthe recording pulse WP used for the irradiation of laser light inaccordance with a signal indicating the calculation result of a logicalproduct of the post-PE modulation diffuse sub-information PRSD and therecording gate signal WG from the timing generator 18 and outputs therecording pulse WP to the optical head 13. The optical head 13intermittently forms the recordable marks by irradiating the laser lighthaving recording intensity on the track of the concave and convex markson the optical disc based on the recording pulse WP. In this way, themedium ID can be intermittently recorded on the track.

By doing so, only one channel bit of the recordable mark can be recordedbetween three channel bits of the concave and convex marks, whereforethe influence on the reproduction accuracy of the concave and convexmarks can be reduced. Further, by intermittently recording therecordable marks, it can be made even more difficult to discriminate therecordable marks by the eyes and to discriminate at which position ofthe optical disc the sub-information is recorded.

Although the recordable mark length is described to be one channel bitof the concave and convex marks in this embodiment, it is not limited tothis. For example, an optical disc recording device normally includes atiming modulator (recording compensation circuit) for modulating theirradiation timing of a recording pulse in units smaller than channelclocks. If this is used, the recordable mark can be formed byirradiating laser light to an area smaller than the channel bit length.If the recordable mark length is equal to or shorter than the shortestlength of the concave and convex marks (2 channel bits in Blu-raydiscs), the concave and convex marks and the recordable mark can beseparated. Thus, the recordable mark may be formed by irradiating laserlight such that the recordable mark length is equal to or shorter thanthe shortest length of the concave and convex marks.

It is also within the scope of the present invention to discretely formthe recordable marks longer than the shortest mark length of the concaveand convex marks. A method for recording the recordable marks longerthan the shortest mark length of the concave and convex marks is asdescribed above. However, in this case, it is desirable to form therecordable marks whose width in the radial direction is narrower thanthe concave and convex marks.

As described above, the medium ID unique to the medium can be recordedon the optical disc by irradiating the laser light on the reflectivefilm on the track of the concave and convex marks using the optical discrecording device of this embodiment. Further, the optical disc recordingdevice of this embodiment can realize the recording of the medium IDwithout requiring constituent elements leading to a considerable costincrease as against a general optical disc recording device. If themedium ID different for each optical disc is used, there can be providedan optical disc enabling the realization of copyright management of anetwork base for managing the medium by an authentication server via anetwork.

Although the method for recording the medium ID of 14 bits in one frameis described in this embodiment, the present invention is not limited tothis. The central aim of the present invention is to record the mediumID in synchronism with the frame structure. For example, the medium IDof 1 bit may be recorded in one frame (in this case, frame=sub-frame) orthe medium ID of 1 bit may be recorded in two frames (in this case,frame<sub-frame).

A method for not recording the recordable marks in synchronization coderecording areas, address recording areas or specific frame areas whichplay an important role in frame synchronization may also be thought. Bydoing so, the deterioration of the reproduction accuracy of the concaveand convex marks can be maximally prevented.

In order to improve the reproduction reliability of the recordable mark,the same bit may be recorded in a plurality of discrete areas aplurality of times. Then, even if there are areas with bad readingaccuracy due to scratch or dust on the optical disc, the readability ofthe medium ID can be improved since the same bit is repeatedly recorded.

If the error correction code is assigned to the medium ID, thereproduction reliability of the medium ID can be further improved. Inthis case, the parity bit for the error correction may be assigned inthe optical disc recording device disclosed in this embodiment or may beassigned by the key management mechanism. If an error detection code isassigned, it is even better since an error correction by parity can bejudged.

(1-4) Optical Disc Reproduction Device According to First Embodiment

FIG. 8 is a block diagram showing the construction of the optical discreproduction device (checking device) used in the checking process ofthe optical disc manufacturing method according to the first embodiment.In the second manufacturing process 300, laser light is irradiated ontothe concave and convex marks to change the reflectivity of thereflective film for the formation of the recordable mark, whereby theoptical disc having the medium ID recorded in a superimposition manneris manufactured. The optical disc reproduction device 7 reproduces themedium ID from the optical disc having the medium ID recorded thereon inthe second manufacturing process 300 and checks whether or not themedium ID is normally recorded on the optical disc.

The optical disc reproduction device 7 shown in FIG. 8 is provided witha spindle motor 12, an optical head 13, a servo circuit 14, an analogsignal processor 15, a digital signal processor 16, a formatter 17, anerror corrector 24, a timing generator 18, a random number generator 19,a PE modulator 21, a LPF 25, a binarizer 26, a correlation integrator27, a memory 11, a reproduction accuracy calculator 28, anauthentication code verifier 29 and a system controller 23. Theconstituent elements of the optical disc reproduction device 7 may bemounted in the same device as the above optical disc recording device 6of the first embodiment.

The spindle motor 12 rotates an optical disc 241 at a rotation speedcorresponding to the optical disc 241 when the optical disc 241 isinserted into the optical disc reproduction device 7.

The optical head 13 irradiates the optical disc 241 with laser lighthaving reproduction intensity when the rotation speed of the insertedoptical disc 241 by the spindle motor 8 reaches a target rotation speed,generates a channel signal CS from the reflected light and outputs it tothe analog signal processor 15.

The analog signal processor 15 extracts a tracking error signal TEindicating a displacement of a laser spot position in the radialdirection and a focus error signal FE indicating a displacement of afocus position of a laser spot in accordance with the channel signal CSinputted from the optical head 13, and outputs them to the servo circuit14. The analog signal processor 15 also extracts an analog reproductionsignal AS corresponding to the concave and convex marks by equalizingthe waveforms of the channel signal CS inputted from the optical head 13or amplifying the channel signal CS, and outputs it to the digitalsignal processor 16 and the LPF 25.

The servo circuit 14 calculates a focus control signal FC for correctingthe displacement of the focus position in accordance with the focuserror signal FE inputted from the analog signal processor 15 and atracking control signal TC for correcting the displacement of thetracking position in accordance with the tracking error signal TE, andoutputs them to the optical head 13. The optical head 13 irradiateslaser light while correcting the focus position and the trackingposition of a laser spot in accordance with these signals. The servocircuit 14 also calculates a linear velocity in accordance with thereproduction signal, generates a rotation control signal SC forcontrolling the rotation speed and outputs it to the spindle motor 12.The spindle motor 12 corrects the rotation speed in accordance with therotation control signal SC inputted from the servo circuit 14.

The digital signal processor 16 is internally provided with a PLL (PhaseLocked Loop) circuit, extracts the clock signal CK synchronized with theanalog reproduction signal AS inputted from the analog signal processor15, samples the analog reproduction signal AS using the extracted clocksignal CK to quantize it, then generates a digital reproduction signalDS by binarizing the quantized analog reproduction signal AS and outputsit to the formatter 17. The digital signal processor 16 also outputs theextracted clock signal CK to the timing generator 18 and the binarizer26.

The formatter 17 detects synchronization patterns assigned at specifiedtime intervals from the digital reproduction signal DS inputted from thedigital signal processor 16 and formats the digital reproduction signalDS into a frame structure. The formatter 17 formats a set including theaddresses of a specified number of frames in address units based on thesynchronization pattern. The formatter 17 also formats in physicalclusters, in which an error correction is made, based on the addresses.The reproduction signal formatted in this way is outputted as formatdata FD to the error corrector 24. The formatter 17 also outputs asynchronization code detection timing signal SY indicating a detectiontiming of the synchronization pattern by the frame to the timinggenerator 18, and outputs the address information ADR assigned to theaddress units to the random number generator 19.

The timing generator 18 generates an initial value set timing signal SETindicating a timing of setting an initial value to a random numbergenerator 19 at the leading end position of the address unit having atarget address where the medium ID is reproduced, and outputs it to therandom number generator 19. In this embodiment, it is assumed that thetarget address is set in the system controller 23 beforehand.

The timing generator 18 includes a counter which operates in accordancewith the clock signal CK inputted from the digital signal processor 16and the synchronization code detection timing signal SY inputted fromthe formatter 17. The counter counts clocks in the frame in synchronismwith the clock signal CK, and resets the held count value at the timingof the synchronization code detection timing signal SY. Further, thecounter includes a counter for adding 1 to the sub-frame unit fordetecting 1 bit of the medium ID (sub-information), and outputs thissub-frame count value CNT to the random number generator 19, thecorrectional integrator 27 and the memory 11. The timing generator 18also generates such a PE modulation signal PE that a front half is “L”and a rear half is “H” in the sub-frame and outputs it to the PEmodulator 21.

The random number generator 19 is constructed by a general M-sequencegeneration circuit including a shift register, and sets the addressinformation ADR inputted from the formatter 17 as an initial value forgenerating the pseudo random sequence RN in the shift register of theM-sequence generation circuit at an output timing of the initial valueset timing signal SET inputted from the timing generator 18. Further,the random number generator 19 generates a pseudo random sequence RN of1 bit by shifting the shift register at the increment timing of thesub-frame count value CNT inputted from the timing generator 18 andoutputs it to the PE modulator 21. It should be noted that the randomnumber generator 19 has the same configuration as the random numbergenerator 19 of the optical disc recording device 6 of this embodiment.

The PE modulator 21 applies a PE modulation to the pseudo randomsequence RN inputted from the random number generator 19 in accordancewith the PE modulation signal PE inputted from the timing generator 18.The PE modulator 21 is constructed by a general XOR gate, generates acorrelation sequence PER by calculating an exclusive OR of the pseudorandom sequence RN and the PE modulation signal PE, and outputs it tothe correlation integrator 27.

The LPF 25 is constructed by a general low-pass filter for limiting theband of the analog reproduction signal AS inputted from the analogsignal processor 15, generates a band-limiting reproduction signal LPSby extracting only low-band components of the analog reproduction signalAS and outputs it to the binarizer 26. The LPF 25 is a filter forpassing the band slower than the longest one of the concave and convexmarks. Thus, the band-limiting reproduction signal LPS limiting the bandindicating the concave and convex marks from the reproduction signal isoutputted from the LPF 25 to the binarizer 26. The binarizer 26 cuts offdirect-current components of the band-limiting reproduction signal LPS,detects a zero-crossing point of the band-limiting reproduction signalLPS in synchronism with the clock signal CK inputted from the digitalsignal processor 16 to generate a binary reproduction signal BS andoutputs it to the correlation integrator 27.

The correlation integrator 27 is internally provided with an up/downcounter, calculates and integrates a correlation between the correlationsequence PER from the PE modulator 21 and the binary reproduction signalBS from the binarizer 26. The up/down counter increments the value of aninternal counter when the correlation between the correlation sequencePER and the binary reproduction signal BS is recognized, i.e. thecorrelation sequence PER is “H” and the binary reproduction signal BS is“H” or the correlation sequence PER is “L” and the binary reproductionsignal BS is “L”.

On the other hand, the up/down counter decrements the value of theinternal counter when the correlation between the correlation sequencePER and the binary reproduction signal BS is not recognized, i.e. thecorrelation sequence PER is “H” and the binary reproduction signal BS is“L” or the correlation sequence PER is “L” and the binary reproductionsignal BS is “H”. Further, the correlation integrator 27 resets thecorrelation integration value to “0” after outputting a held correlationintegration value CIN to the memory 11 at the increment timing of thesub-frame count value CNT inputted from the timing generator 18.Accordingly, an integration value of the correlation sequence PER andthe binary reproduction signal BS in the sub-frame as the range fordetecting 1 bit of the medium ID is outputted to the memory 11.

The memory 11 adds the correlation integration value CIN inputted fromthe correlation integrator 27 to a value stored in a memory spacecorresponding to the sub-frame count value CNT inputted from the timinggenerator 18 and stores it. Thus, the memory 11 has memory spacescorresponding to all the bits of the medium ID and an integration valueof each bit of the medium ID is stored during the reproduction of themedium ID.

The authentication code verifier 29 inputs a code bit of the integrationvalue corresponding to each bit of the medium ID in the memory 11 asmedium information. Specifically, the authentication code verifier 29calculates a bit value of “0” when the integration value is “+” and abit value of “1” when the integration value is “−”. The authenticationcode verifier 29 judges whether the read medium ID is normal or alteredbased on the authentication code assigned to the calculated medium ID. Adigital signature or MAC is used as this authentication code, and theauthentication code verifier 29 judges whether or not the digitalsignature is normally verified or whether or not the assigned MAC isnormal. The authentication code verifier 29 outputs the extracted mediumID if the authentication code is judged to be normal or continues toperform the reproduction operation if the authentication code is judgednot to be normal. If no normal medium ID is detected even if thereproduction operation is continued for longer than a specified time,the optical disc is ejected as an illegal disc or a defective disc andthe reproduction operation is ended. If parity for error correction orerror detection is assigned to the medium ID, the continuation of thereproduction operation may be judged based on this parity. In otherwords, the authentication code verifier 29 extracts the medium ID fromthe code bit of the memory and performs an error correction or errordetection using the assigned parity. The reproduction operation iscontinued if an error is judged, and the digital signature or the MAC isverified if no error is judged.

The reproduction accuracy calculator 28 receives the integration valuescorresponding to the respective bits of the medium ID from the memory11, calculates an average absolute value and a standard deviation of theintegration values, estimates a bit error rate of the medium ID from aGaussian distribution based on the average and the standard deviation,and judges whether or not the medium ID is normally recorded by judgingthe estimated bit error rate using a threshold value. If the bit errorrate is below the threshold value, i.e. the medium ID is judged not tobe normally recorded, the disc being reproduced is ejected as adefective disc. The above bit error rate can be estimated by integrationfrom −∞ to 0 of the above Gaussian distribution.

In this embodiment, the spindle motor 12, the optical head 13, the servocircuit 14 and the analog signal processor 15 correspond to an exampleof a tracking unit, the analog signal processor 15 to an example of areproduction signal extracting unit, the digital signal processor 16 toan example of a clock extracting unit, the LPF 25 and the binarizer 26to an example of a separating unit, the formatter 17, the timinggenerator 18, the random number generator 19, the PE modulator 21, thecorrelation integrator 27 and the memory 11 to an example of asub-information reproducing unit, the formatter 17 to an example of asynchronization code detector, the LPF 25 to an example of aband-limiting filter, the random number generator 19 to an example of acorrelation sequence generator, the correlation integrator 27 to anexample of a correlation detector and the authentication code verifier29 to an example of a reproducing unit.

Next, the operation of the optical disc reproduction device 7 isdescribed in detail. FIG. 9 is a timing chart showing a characteristicoperation of the optical disc reproduction device according to the firstembodiment. In the following description, the optical disc is a Blu-rayROM disc.

The digital reproduction signal DS outputted from the digital signalprocessor 16 of the optical disc reproduction device 7 is reproduced asconsecutive physical clusters as units of error correction (64 kilobytesin user data). Each physical cluster is comprised of 16 address unitsassigned with the address information ADR. The address unit is made upof 31 frames each assigned with a synchronization code, and 1 frame ismade up of 1932 channel bits.

Here, if the target address where the detection of the medium ID isstarted is “N”, the timing generator 18 outputs the initial value settiming signal SET to the random number generator 19 at the leading endposition of the address unit assigned with the address “N”, and theformatter 17 outputs the address “N” to the random number generator 19.

The timing generator 18 includes a counter for adding 1 by the sub-frame(1 sub-frame is 138 channel bits) for detecting 1 bit of the medium IDin one frame, and outputs the count value of this counter as thesub-frame count value CNT to the random number generator 19, thecorrelation integrator 27 and the memory 11.

The random number generator 19 sets the address “N” outputted from theformatter 17 as an initial value in the internal shift register at anoutput timing of the initial value set timing signal SET from the timinggenerator 18. The random number generator 19 also generates a pseudorandom sequence RN bit by bit by shifting the internal shift register atthe increment timing of the sub-frame count value CNT from the timinggenerator 18 and outputs it to the PE modulator 21.

The timing generator 18 generates such a PE modulation signal PE thatfirst 69 channel bits are “L” and the following 69 channel bits are “H”,and outputs it to the PE modulator 21. The PE modulator 21 generates therandom sequence PER by calculating an exclusive OR of the PE modulationsignal PE inputted from the timing generator 18 and the pseudo randomsequence RN outputted from the random number generator 19, and outputsit to the correlation integrator 27.

FIG. 9 shows recording modes of three types of recordable marks SMK, andthe concave and convex marks MK on the optical disc and the recordablemarks SMK having the reflectivity changed by the irradiation of laserlight are shown in any of these recording modes. At any rate, thereflected light level indicated by the analog reproduction signal ASoutputted from the analog signal processor 15 is averagely larger in apart where the recordable marks SMK are recorded than in a part where norecordable marks are recorded. This is because the reflective filmapplied to the optical disc has such a characteristic to increase thereflectivity by the irradiation of laser light.

A modulation factor r2 influential to the reflected light intensity ofthe recordable marks SMK is smaller than a modulation factor r1 of thereflected light level of the concave and convex marks MK. Desirably, ifthe modulation factor r2 of the reflected light level of the recordablemarks SMK is equal to or below ½ (half) the modulation factor r1 of thereflected light level of the concave and convex marks MK, the influenceof the recording of the recordable marks SMK on the reproductionaccuracy of the concave and convex marks MK can be made rare. The aboverelationship of the reflected light levels can be realized by adjustingthe laser intensity or adjusting the irradiation time of the laser lightupon recording the recordable marks SMK to make the width of therecordable marks SMK in the track direction smaller than that of theconcave and convex marks MK in the track direction.

Also when the recordable mark SMK is present between the tracks of theconcave and convex marks MK as shown in FIG. 9, the laser spot at thetime of reading the concave and convex marks MK is normally wider thanthe width of the concave and convex marks MK in the track direction, andthe characteristic of the reflected light level of the analogreproduction signal AS changes in the area where the recordable mark SMKis formed.

Also in the case of discretely arranging the recordable marks SMK, thereflectivity is higher in the part where the recordable marks SMK areformed to change the characteristic of the reflected light level of theanalog reproduction signal AS.

Normally, the optical disc reproduction device often includes aso-called baseline control circuit for detecting an error of azero-crossing point of the analog reproduction signal AS and pursuingthe error for correction. However, the recordable mark SMK in thisembodiment is formed by the sub-frame (=138 channel bits=about 480 KHzat a 1× speed of the Blu-ray disc) and outside the pursuit band of thenormal baseline control circuit. Thus, the zero-crossing point iscorrected and there is no likelihood of making it impossible toreproduce the recordable marks SMK.

The LPF 25 is constructed by a band-limiting circuit (filter) forapplying a passband limitation to the analog reproduction signal ASinputted from the analog signal processor 15 and, in this embodiment, isrealized by a low-pass filter in which a band higher than the band ofthe sub-frames and lower than that of a combination of the mark and landof the longest mark length of the concave and convex mark is set as acutoff frequency. The band-limiting reproduction signal LPS obtained bypassing the LPF 25 is “H” in the parts where the recordable marks SMKare formed and “L” in the parts where no recordable mark SMK is formed.

The binarizer 26 generates the binary reproduction signal BS bycalculating and binarizing the zero-crossing point while synchronizingthe band-limiting reproduction signal LPS inputted from the LPF 25 withthe clock signal CK from the digital signal processor 16, and outputs itto the correlation integrator 27.

The correlation integrator 27 integrates the correlation values of thebinary reproduction signal BS from the binarizer 26 and the correlationsequence PER from the PE modulator 21 within the range of the sub-frameindicated by the sub-frame count value CNT of the timing generator 18,and outputs the integration value to the memory 11. In other words, thecorrelation integrator 27 judges the correlation between the binarizedsignal BS and the correlation sequence PER and increments the countvalue of the internal up/down counter in synchronism with the clocksignal CK when the correlation sequence PER is “H” and the binaryreproduction signal BS is “H” or the correlation sequence PER is “L” andthe binary reproduction signal BS is “L”.

On the other hand, the correlation integrator 27 judges no correlationbetween the binarized signal BS and the correlation sequence PER anddecrements the count value of the internal up/down counter when thecorrelation sequence PER is “H” and the binary reproduction signal BS is“L” or the correlation sequence PER is “L” and the binary reproductionsignal BS is “H”. The correlation integrator 27 repeatedly performs thiswithin the sub-frame to calculate the integration value corresponding to1 bit of the medium ID. The correlation integrator 27 also outputs theinternally held correlation integration value CIN of 1 bit to the memory11 at the increment timing of the sub-frame count value CNT from thetiming generator 18, and resets the internally held integration value.

The memory 11 adds the correlation integration value CIN of 1 bitinputted from the correlation integrator 27 to the value stored in thememory space indicated by the sub-frame count value CNT inputted fromthe timing generator 18.

The authentication code verifier 29 receives the code bit of the memory11 corresponding to 1 bit of the medium ID and confirms whether or notthe readout is normally made based on the assigned authentication codeor error correction code. The system controller 23 ends the reproductionoperation when the normal readout of the medium ID is confirmed as aresult of verification by the authentication code verifier 29. On theother hand, the system controller 23 continues the reproductionoperation to continue the integration operation of each bit of themedium ID if the authentication code verifier 29 judges fraud byverifying the digital signature or the MAC or judges incapability oferror correction or the presence of an error bit. Further, the systemcontroller 23 ejects the optical disc as an illegal disc if the normalreadout of the medium ID was impossible within a designated time range.

The reproduction accuracy calculator 28 obtains the integration valuesof the respective bits of the medium ID from the memory 11, calculatesan average value and a standard deviation of the absolute values of theintegration values of the respective bits, estimates a bit error rate ofthe medium ID by approximating these calculated average value andstandard deviation to a Gaussian distribution, and verifies the opticaldisc based on the bit error rate. The reproduction accuracy calculator28 judges the optical disc to have poor reading accuracy of the mediumID if the bit error rate is equal to or higher than a specified value asa result of verification. The optical disc judged to have poor readingaccuracy is ejected.

In the checking process for checking the reading accuracy of the mediumID, a judgment criterion for the judgment of an illegal disc needs to beset sufficiently low. This is because there is reliability variation inthe readout of the medium ID among optical disc reproduction devices.Thus, the specified value sufficiently taking account of this needs tobe set. Although the reliability in the reading accuracy of the mediumID is estimated based on the average and variation of the integrationvalues stored in the memory 11 in this embodiment, the present inventionis not particularly limited to this and the reliability may be estimatedmerely from the average value since the variation is uniquely outputtedin optical discs to a certain extent.

An integration time until the authentication code verifier 29 judgesthat the error correction is possible or no error bit is present in themedium ID may be used as an indicator of the reliability in the readingaccuracy of the medium ID. This is because the integration time for thereadout is short if the recording accuracy of the medium ID is goodwhile being long if the recording accuracy is poor. For example, if theintegration values of the respective bits of the medium ID completelyform a Gaussian distribution, time four times as long is required toread the medium ID at the same accuracy if the signal components of themedium ID are halved.

As described above, the optical disc reproduction device 7 according tothis embodiment reproduces the main information of the concave andconvex marks from the optical disc having the medium ID recorded thereonby the recordable marks formed by changing the reflectivity of thereflective film on the concave and convex marks and, at the same time,reproduces the medium ID by integrating the fluctuation of the reflectedlight level of the reproduction signal. Further, the recording accuracyof the medium ID is judged based on the average value and variation ofthe integration values of the respective bits of the medium ID or thetime until the readout of the medium ID is completed, and the opticaldisc judged to have poor recording accuracy is ejected as an illegaldisc. Further, the medium ID is recorded in the form of the digitalsignature information, MAC or error correction code, the integrationoperation is continued, assuming no sufficient integration, if thedigital signature cannot be verified, the MAC cannot be verified or theerror cannot be corrected, and ejects the optical disc by judging it asan illegal disc if the integration time is longer than the specifiedtime.

In this embodiment, the recording position where the medium ID is to berecorded is not limited to the control region CTL and may be a userregion USR on the optical disc or any region where the addressinformation is recorded in the form of concave and convex marks.

Although the optical disc according to this embodiment is described as aread-only optical disc having information recorded thereon by theconcave and convex marks, the present invention is not limited to this.In a recordable disc or rewritable disc including a wobble track andformed with a recordable film or a phase change film as well, it ispossible to record a medium ID by irradiating laser light to a regionwhere main information was recorded by irradiating laser light. In thisway, the medium ID can be recorded on the recordable disc and therewritable disc. On these discs, if the medium ID can be recorded as anencryption key of the main information, an optical disc recordable bychanging the key for each recording, whereby copyright protection can befurther improved.

If the present invention is applied, the medium ID can be recorded evenon a read-only optical disc, wherefore network copyright management canbe realized. Specifically, frequency information on the reproduction,transfer or copy of contents recorded on optical discs is managed by amanagement server connected via a network. Thus, even if the opticaldisc is a read-only optical disc, a using method convenient to userssuch as the copy of content on another medium such as a hard disc forthe backup purpose or the transfer of the content to the hard disc forviewing and listening purpose can be provided. For example, when thecontent is transferred from the optical disc to the hard disk, themedium ID of the optical disc is transmitted to the management server atthe time of the transfer and the transfer of the content is recordedwhile being related to the medium ID in the management server. Uponreceiving a request to permit the reproduction of the content includingthe medium ID, the management server judges that the content was alreadytransferred based on the management information stored therein, anddismisses this reproduction request. By building such a system, anenvironment capable of transferring contents while protecting copyrightscan be provided.

Second Embodiment (2-1) Optical Disc According to Second Embodiment

FIG. 10 is a conceptual diagram showing the construction of an opticaldisc according to a second embodiment. The optical disc 1 shown in FIG.10 includes a clamp region CLP to be clamped upon loading the opticaldisc 1 into an optical disc recording device or an optical discreproduction device, two control regions CTL at inner and outercircumferential sides where information on copyright, a physicalcharacteristic of the optical disc 1 or management information of theoptical disc 1 is recorded in the form of concave and convex marks, anda user region USR where, for example, encrypted movie title or PC datainformation is recorded in the form of concave and convex marks.

At least the user region USR and the control regions CTL of the opticaldisc 1 are formed by transferring the concave and convex marks to anoptical disc substrate 1P made of polycarbonate or the like, applying areflective film 1L, whose reflectivity changes by the irradiation oflaser light, on the concave and convex marks, and then applying aprotective film IC.

In the control region CTL at the inner circumferential side of theoptical disc 1, premarks PM formed by changing the reflectivity of thereflective film on the concave and convex marks MK or removing thereflective film by the irradiation of laser light, long in radialdirections of the optical disc and crossing the track formed by theconcave and convex marks are formed after the reflective film of theoptical disc is applied. Further, the length of the recorded premarks PMin a circumferential direction is longer than the longest one of theconcave and convex marks MK. The premarks PM may be recording markswhose reflectivity increases or decreases by the irradiation of laserlight or may be non-reflective marks, for example, in the case ofremoving the reflective film.

In regions with the address information of the optical disc, i.e. atleast in the control regions CTL and the user region USR, recordablemarks are formed by irradiating laser light onto the track of theconcave and convex marks MK similar to the medium ID recording method ofthe first embodiment after the disc shaping and the recording of thepremarks PM, whereby distances from address positions recorded by theconcave and convex marks to the premarks PM are recorded as physicalposition information. Further, the physical position informationincludes addresses as reference positions of the concave and convexmarks PM, and a set of at least two points distanced by a specifieddistance in the radial direction are recorded for one premark PM.

Thus, in the control regions CTL of the optical disc 1 of thisembodiment, the concave and convex marks MK including the addresses aretransferred, and the premarks PM are recorded by changing thereflectivity of the reflective film or moving the reflective filmremoved by irradiating the laser light to the reflective film. Further,the radial distances from the address positions as references of theconcave and convex marks MK to the premarks PM are obtained as thephysical position information. The physical position information isdetected twice or more at different radial positions with respect to onePremark PM. The physical position information is recorded as therecordable mark formed by irradiating laser light based on the track ofthe concave and convex marks MK in an address recorded area of at leastthe user region USR or the control regions CTL to change thereflectivity of the reflective film on the tracks.

The premarks PM in this embodiment are long in the radial directions ofthe optical disc. Accordingly, in the case of copying them, all of therecording start position, rotation speed, linear velocity and the likeof the optical disc need to be identical between a copy destination anda copy source. If these differ even slightly, a reproduction position(angular position) at the copy source and a recording position (angularposition) at the copy destination are displaced, whereby it becomesimpossible to copy the premarks PM as recording marks straight in theradial directions. Therefore, it is very difficult to copy such marks asthey are.

At the time of recording, a distance (physical position information)from the reference address position to the premark PM is measured by areproduction clock and recorded as a recordable mark on the concave andconvex marks. For one premark PM, the physical position information fromat least one reference address to two points distanced by several tracksin the radial direction is recorded. At the time of reproduction, therecordable mark is reproduced to obtain the physical positioninformation of the target address and at least two points at the time ofrecording, and the obtained physical position information from thetarget address to the premark is confirmed at least at the same twopoints as at the time of recording.

Accordingly, unless the optical disc is an illegally duplicated opticaldisc, there is a correlation between the physical position informationat the time of recording and the one at the time of reproduction and thereproduction of the optical disc is permitted. On the other hand, thereis no correlation between them, the optical disc is judged to be anillegally duplicated optical disc and the reproduction of the opticaldisc is not permitted. By comparing the pieces of physical positioninformation from one address position to at least two points of onepremark PM, it can be judged whether or not the premark PM is straightin the radial direction. Normally, if the recording position of the copysource and that of the copy destination are displaced due to illegalcopying, the premark PM having lost linearity in the radial direction isduplicated. Since the linearity is judged by verifying the physicalposition information on at least two points in this way, resistance toillegal copying can be improved.

Further, a plurality of premarks PM may be provided on a circumferenceof the optical disc 1. By confirming the physical position informationof all of these premarks PM, resistance to illegal copying can beimproved.

Although the recording positions of the premarks PM are described to belocated in the control region CTL at the inner circumferential side inthis embodiment, they may be located in the control region CTL at theouter circumferential side, the user region USR or any region where theaddress information is recorded.

The recording positions of the premarks PM and those of the recordablemarks are preferably distanced from each other by a specified radialdistance. This is because it becomes difficult to separate these piecesof information if they are recorded in the same region since they areboth recorded by changing the reflectivity of the reflective film.

(2-2) Optical Disc Manufacturing Method According to Second Embodiment

FIG. 11 is a diagram showing an optical disc manufacturing methodaccording to the second embodiment. By the optical disc manufacturingmethod according to the second embodiment, an optical disc ismanufactured in the procedure of an authoring process 100, a firstmanufacturing process 200, a second manufacturing process 500, a thirdmanufacturing process 600 and a fourth manufacturing process 700.

The authoring process 100 is a process similar to the authoring process100 of the first embodiment, and content data to be recorded on theoptical disc is authored in a disc format. The content data to berecorded is encrypted using an encryption key generated by a keymanagement mechanism, and encrypted content data is authored andoutputted to the first manufacturing process 200.

The first manufacturing process 200 is a process similar to the firstmanufacturing process 200 of the first embodiment, and an input step201, a mastering step 202, a stamping step 203, a sputtering step 204and a protective film applying step 205 are successively performed inthis order to produce an optical disc 40 having no physical positioninformation recorded thereon. Specifically, in the input step 201, thecontent data generated in the authoring process 100 is inputted. In themastering step 202, a disc master is produced. In the stamping step 203,a stamper is formed to stamp the optical disc substrate, whereby concaveand convex recording marks are transferred. In the sputtering step 204,a reflective film whose reflectivity changes by the irradiation of laserlight is deposited on the concave and convex marks. In the protectivefilm applying step 205, an optical disc 40 having a protective filmapplied on the concave and convex marks is produced. The producedoptical disc 40 is transferred to the second manufacturing process 500.

In the second manufacturing process 500, a premark recording device 70records straight premarks in radial directions by irradiating laserlight at radial positions corresponding to the control region CTL at theinner side of the optical disc. The premark recording device 70 rotatesthe optical disc by a CAV (Constant Angular Velocity) control when theoptical disc 40 produced in the first manufacturing process 20 isloaded. The premark recording device 70 moves an optical head to theradial position where the premark is to be recorded when the opticaldisc 40 reaches a specified rotation speed, intermittently irradiatesthe laser light in synchronism with a rotation synchronization signalsynchronized with one rotation of the disc, and moves the optical headby a specified amount toward the outer circumferential side every timethe optical disc makes one rotation. By repeatedly performing this, thepremark long in the radial direction is formed on the optical disc 40.

The premark recording device 70 may form the premark by irradiatingsemiconductor laser light to change the reflectivity of the reflectivefilm or may form the premark by trimming the reflective film through theirradiation of a beam by an initializer employing a YaG laser. Anoptical disc 50 having the premarks formed in the control region CTL atthe inner circumferential side of the optical disc in the secondmanufacturing process 500 is transferred to the third manufacturingprocess 600.

In the third manufacturing process 600, the physical positioninformation of the premarks are measured based on the addressinformation by the concave and convex marks from the optical disc 50having the premarks formed in the second manufacturing process 500.

A physical position information acquiring device 80 moves an opticalhead to the radial position, where the premark is formed, in the controlregion CTL at the inner circumferential side when the optical disc 50formed with the premarks in the second manufacturing process 500 isloaded. Subsequently, the physical position information acquiring device80 measures the physical position information of the premarks on theoptical disc based on the address information recorded by the concaveand convex marks. The physical position information is a clock numberfrom the reference address position to the starting position of thepremark calculated by counting reproduction clocks at the time ofreproducing the concave and convex marks. In other words, the physicalposition information acquiring device 80 acquires the physical positioninformation as information on a distance from the reference addressposition or an angle.

The physical position information acquiring device 80 measures at leasttwo points of premark position distanced from one address referenceposition by a specified distance in the radial direction and outputsthem in correspondence with reference address information to the fourthmanufacturing process 700.

The physical position information acquiring device 80 also detects thephysical position information of two or more premarks when a pluralityof premarks are present in the circumferential direction and outputs itto the fourth manufacturing process 700.

The fourth manufacturing process 700 is a process similar to the secondmanufacturing process 300 of the first embodiment. Although the mediumID is recorded by changing the reflectivity of the reflective filmthrough the irradiation of laser light from a specified address positionin the first embodiment, this embodiment differs in that the physicalposition information acquired in the third manufacturing process 600 isfurther recorded. Since an optical disc recording device 6 similar tothe one used in the second manufacturing process 300 of the firstembodiment is used in the fourth manufacturing process 700, it is notdescribed in detail in this embodiment.

FIG. 12 is a diagram showing a data format of the physical positioninformation indicating from the reference address positions to thepositions of the premarks detected in the third manufacturing process600 and outputted to the fourth manufacturing process 700. Physicalposition information 90 includes a medium ID 91, premark positioninformation 92 and an alteration preventing code 93.

The medium ID 91 is similar to the medium ID of the first embodiment andindividual identification information of each optical disc issued fromthe key management mechanism.

The premark position information 92 is data relating the clock number ofthe reproduction clock up to the starting position of the premark andthe address position of the concave and convex mark based on the addressinformation recorded by the concave and convex marks in the thirdmanufacturing process 600 of the optical disc manufacturing method. If aplurality of premarks are recorded in the circumferential direction, thepremark position information 92 includes reference addressescorresponding to the respective premarks. The premark positioninformation 92 on at least two points distanced from the same premarkdistanced by a specified radial distance is detected from one addressposition. In other words, a premark starting position 1A and a premarkstarting position 1B are in correspondence with a reference address 1 inthe premark position information 92 of FIG. 12. The premark startingposition 1A is the starting position of the premark detected on the sametrack as the reference address, and the premark starting position 1B isthe starting position of the premark acquired upon moving several trackstoward the outer or inner circumferential side from the referenceaddress 1.

The alteration preventing code 93 is, for example, a MAC (MessageAuthentication Code). For example, a hash value of the medium ID 91 andthe premark position information 92 is calculated and generated as aMAC. Key information used for the generation of the hash value isobtained from the key management mechanism. At the time of reproduction,a hash value is similarly calculated based on the medium ID 91 and thepremark position information 92, it is judged whether or not thephysical position information was altered by comparing the calculatedhash value and the hash value (alteration preventing code 93) includedin the physical position information, and the reproduction operation iscontinued only when no alteration is judged.

As described above, according to the optical disc manufacturing methodaccording to the second embodiment, the straight premark is recorded inthe radial direction in the control region CTL at the innercircumferential side after the optical disc having the content datarecorded by the concave and convex marks is produced, the physicalposition information of this premark is detected based on the addressposition recorded by the concave and convex marks, the recordable markwhose reflectivity is changed by the irradiation of laser light onto thetrack of the concave and convex marks is formed, and the physicalposition information is recorded by the recordable mark.

It is desirable to incorporate the premark recording device, thephysical position information acquiring device and the optical discrecording device used in the optical disc manufacturing method accordingto the second embodiment into the same device, but these devices aredescribed as separate devices in order to simplify the description ofthe respective functions here.

The premark long in the radial direction is recorded on the optical discof the second embodiment, the physical position information of thispremark is measured in the manufacturing process and the measuredphysical position information is recorded as the recordable mark. Asdescribed above, in order to copy the premark long in the radialdirection, it is necessary to accurately control the recording startingposition, the rotation speed and the linear velocity at the copy sourceand the copy destination. However, it is virtually impossible to matchthese factors at both sides, wherefore illegal duplication can beeliminated. Further, since the physical position information of thepremark is recorded by the method similar to the medium ID recordingmethod of the first embodiment, the optical disc of the secondembodiment has drastically higher resistance to illegal duplication ascompared to the first embodiment.

(2-3) Premark Recording Device According to Second Embodiment

FIG. 13 is a block diagram showing the construction of a premarkrecording device used in the second manufacturing process 500 of theoptical disc manufacturing method of the second embodiment.

The premark recording device 70 is provided with a spindle motor 12, anoptical head 13, an analog signal processor 15, a servo circuit 14, aPLL circuit 30, a counter 31, a recording timing generator 32, a laserintensity modulator 22 and a system controller 23.

The spindle motor 12 rotates the optical disc 40 by a CAV (ConstantAngular Velocity) control when the optical disc 40 having the physicalposition information generated in the first manufacturing process 200not yet recorded is inserted into a drive. The spindle motor 12 alsogenerates a rotation synchronization signal FS to be outputted aplurality of times in synchronism with one rotation of the disc andoutputs it to the PLL circuit 30.

The optical head 13 irradiates the optical disc 40 with laser light,generates a channel signal CS from the reflected light and outputs it tothe analog signal processor 15.

The analog signal processor 15 generates a focus error signal FEindicating a displacement of a focus position, to which the laser lightis irradiated, from the channel signal CS inputted from the optical head13 and outputs it to the servo circuit 14.

The servo circuit 14 generates a focus control signal FC for controllingthe focus position from the focus error signal FE inputted from theanalog signal processor 15, and outputs it to the optical head 13. Thus,the optical head 13 irradiates the laser light while correcting thefocus position.

The PLL circuit 30 generates a rotation synchronizing clock CAVCKpursuing the rotation synchronization signal FS synchronized with onerotation of the disc from the spindle motor 12 and outputs it to thecounter 31. One rotation synchronization signal FS may be output perrotation, but it is desirable to output a plurality of rotationsynchronization signals FS per rotation. For example, if the rotationsynchronization signal FS is outputted four times per rotation, therotation synchronization signal is outputted at every rotation angle of45°. If the rotation synchronization signal FS is outputted 360 timesper rotation, the rotation synchronization signal is outputted at everyrotation angle of 1°. The PLL circuit 30 generates the rotationsynchronizing clock CAVCK pursuing these rotation synchronizationsignals FS. If only about one rotation synchronization signal FS can beobtained per rotation, it is desirable to increase the frequency of therotation synchronizing clock CAVCK to be outputted using a multiplyingcircuit after the rotation synchronizing clock CAVCK synchronized withthe rotation synchronization signal FS is generated.

The counter 31 counts the rotation synchronizing clocks CAVCK outputtedfrom the PLL circuit 30. In other words, the counter 31 equivalentlycounts the rotational angle of the disc. The counter 31 is reset uponone rotation of the disc. In other words, the counter 31 is reset uponcounting 360 if the rotation synchronization signal FS is outputted 360times per one rotation of the disc. The count value of this counter 31is outputted as the rotation synchronizing clock count value CAVCNT tothe recording timing generator 32.

The recording timing generator 32 generates a timing of irradiatingrecording laser light based on the rotation synchronizing clock countvalue CAVCNT from the counter 31. For example, the recording timinggenerator 32 generates a premark recording timing signal PMWG bydetecting a timing at which the remainder is 0 when the rotationsynchronizing clock count value CAVCNT is divided by 90. Thus, therecording timing generator 32 generates the premark recording timingsignal PMWG four times per one rotation of the disc and within therotational angle range of 1°. The premark recording timing signal PMWGgenerated by the recording timing generator 32 is outputted to the laserintensity modulator 22.

The light intensity modulator 22 increases the amount of a currentflowing into a laser to generate a premark recording pulse PWP forirradiating laser light with a recording power at an output timing ofthe premark recording timing signal PMWG from the recording timinggenerator 32 and outputs it to the optical head 13. In parts where thepremark recording timing signal PMWG is not outputted, the premarkrecording pulse PWP for irradiating the laser light having reproductionintensity is outputted.

The optical head 13 moves a laser spot position toward the outercircumferential side by a specified amount per one rotation of the disc.The specified amount is set equal to or shorter than the length in theradial direction of the premark recorded by one rotation through theirradiation of laser light. Thus, the premark straight and continuous inthe radial direction of the optical disc can be recorded.

As described above, the premark recording device 70 controls therotation of the optical disc by the CAV control after the optical dischaving the concave and convex marks transferred thereto is produced, andirradiates the laser light based on the angular information (here,rotation synchronizing clock count value CAVCNT) of the optical disc. Inthis way, the premark long in the radial direction can be recorded.

The premark recording device 70 may employ a high-output YaG laser orthe like instead of the semiconductor laser. In such a case, it is knownthat the reflective film in a part irradiated with the laser light ismelted and removed.

(2-4) Physical Position Information Acquiring Device According to SecondEmbodiment

FIG. 14 is a block diagram showing the construction of the physicalposition information acquiring device used in the third manufacturingprocess 600 of the optical disc manufacturing method according to thesecond embodiment.

The physical position information acquiring device 80 extracts theaddress of the concave and convex mark at the radial position where thepremark is recorded from the optical disc recorded with the premark inthe second manufacturing process 500 of the second embodiment, anddetects the starting point of the premark based on the extracted addressas the physical position information. The physical position informationacquiring device 80 is provided with a spindle motor 12, an optical head13, a servo circuit 14, an analog signal processor 15, a digital signalprocessor 16, a formatter 17, an error corrector 24(A)D33, a slicer 34,a counter 35, a memory 11, a medium ID assignor 36, an alterationpreventing code assignor 37 and a system controller 23.

The spindle motor 12 rotates an optical disc 50 at a rotation speedcorresponding to the optical disc 50 when the optical disc 50 recordedwith the premark is inserted, and moves the optical head 13 to aspecified radial position where the premark is recorded.

The optical head 13 irradiates the optical disc 50 with laser lighthaving reproduction intensity when the spindle motor 12 reaches aspecified rotation speed, generates a channel signal CS from thereflected light and outputs it to the analog signal processor 15.

The analog signal processor 15 generates a tracking error signal TEindicating a displacement of a tracking position of a laser spot withrespect to the track of the concave and convex marks and a focus errorsignal FE indicating a displacement of a focus position of the laserspot in accordance with the channel signal CS inputted from the opticalhead 13, and outputs them to the servo circuit 14. The analog signalprocessor 15 also generates an analog reproduction signal AScorresponding to the concave and convex marks by equalizing thewaveforms of the channel signal CS inputted from the optical head 13 oramplifying the channel signal CS, and outputs it to the digital signalprocessor 16.

The servo circuit 14 generates a tracking control signal TC forcorrecting the tracking position of the laser spot in accordance withthe tracking error signal TE inputted from the analog signal processor15 and a focus control signal FC for correcting the focus position inaccordance with the focus error signal FE, and outputs them to theoptical head 13. The optical head 13 irradiates laser light whilecorrecting the tracking position and the focus position in accordancewith these control signals. The servo circuit 14 also generates arotation control signal SC by comparing the rotation speed correspondingto the radial position and the current rotation speed, and outputs it tothe spindle motor 12. The spindle motor 12 controls the rotation speedin accordance with the rotation control signal SC to rotate the opticaldisc 50.

The digital signal processor 16 is internally provided with a PLLcircuit and extracts a clock signal CK synchronized with the analogreproduction signal AS inputted from the analog signal processor 15. Thedigital signal processor 16 also generates a binary digital reproductionsignal DS by quantizing the analog reproduction signal AS inputted fromthe analog signal processor 15 in synchronism with the clock signal CK,and outputs it to the formatter 17.

The formatter 17 detects synchronization codes assigned at specifiedtime intervals from the digital reproduction signal DS inputted from thedigital signal processor 16 and formats by the frame that is a group ofdata assigned with the synchronization codes. The formatter 17discriminates frame positions by judging the synchronization pattern ofthe synchronization codes, and divides into address units each comprisedof a plurality of frames and assigned with address information ADR. Theformatter 17 also formats into physical clusters as units of errorcorrection based on the address information ADR to generate format dataFD, and outputs it to the error corrector 24. Further, the formatter 17extracts a frame pulse FPLS indicating the timing of the synchronizationcode and the address information ADR assigned to each address unit, andoutputs them to the counter 35.

The error corrector 24 separates parity for error correction from theformat data FD inputted from the formatter 17 and performs an errorcorrection to the data, whereby reproduction data recorded by theconcave and convex marks is outputted.

The AD 33 is constructed by a general analog-to-digital converter, andoutputs a quantized reproduction signal RD to the slicer 34 byquantizing the analog reproduction signal AS inputted from the analogsignal processor 15 in synchronism with the inputted clock.

The slicer 34 generates a binary premark detection signal PMDET byslicing the inputted quantized reproduction signal RD at a specifiedslice level, and outputs it to the counter 35. The specified slice levelis set higher or lower than a slice level for binarization of thedigital signal processor 16 in the physical position informationacquiring device 80. This is determined whether the premark is recordedby increasing the reflectivity through the irradiation of laser light orrecorded as a non-reflective mark by removing the reflective film. Thespecified slice level is not a fixed value and preferably automaticallyset by scanning the premark several times.

The counter 35 includes a channel bit counter for counting the clocksignal CK inputted from the digital signal processor 16 and a framecounter for counting the number of frames.

The channel bit counter counts the number of clocks in synchronism withthe clock signal CK inputted from the digital signal processor 16 and isreset by a frame pulse FPLS indicating the starting position of theframe inputted from the formatter 17.

The frame counter counts the frame pulse FPLS inputted from theformatter 17 and is reset at a timing at which the address informationADR inputted from the formatter 17 is updated.

The counter 35 generates premark position information POS based on thecurrent count values of the channel bit counter and the frame counterand the address information ADR inputted from the formatter 17 at aninput timing of the premark detection signal PMDET from the slicer 34,and outputs it to the memory 11.

The memory 11 temporarily saves the premark position information POSoutputted from the counter 35. If a plurality of premarks are recordedin the circumferential direction of the optical disc, pieces of premarkposition information POS corresponding to the respective premarks aremeasured and saved.

The medium ID assignor 36 relates the medium ID inputted from theoutside to the premark position information POS saved in the memory 11when the detection of the premark of the optical disc is completed.

The alteration preventing code assignor 37 calculates hash values of themedium ID and the premark position information POS using a key givenfrom the outside or secretly saved inside to generate an alterationpreventing code (e.g. MAC), and generates the physical positioninformation by assigning the generated alteration preventing code to themedium ID and the premark position information POS. This physicalposition information is outputted to the fourth manufacturing process700 of the second embodiment.

As described above, it more effectively prevents the illegal duplicationto measure the premark position information POS at two positionsdistanced in a specified radial direction from the same address for onepremark. In this case, the formatter 17 jumps one track toward the innercircumferential side and reproduces the track at the same addressposition again after detecting the starting position of the premark onthe same track as the reference address position, generates a track jumpsignal TJ for moving the track position several tracks toward the outeror inner circumferential side again at the timing of the referenceaddress and outputs it to the servo circuit 14.

The servo circuit 14 moves the tracking position several tracks towardthe outer or inner circumferential side in accordance with the trackjump signal TJ. Upon the completion of a track jump, the premarkposition is judged from the reproduction signal, whereby the premarkposition can be detected at a plurality of positions distanced by thespecified radial distance from one premark.

The physical position information acquiring device 80 extracts thephysical position information from the reference address to the premarkstarting position by counting the clock signal CK at the time ofreproduction. Accordingly, if the clock signal CK at the time ofreproduction is disturbed by the track jump, it is impossible to detectthe correct physical position information. Accordingly, the formatter 17generates a PLL hold signal for locking the oscillation frequency of theclock signal CK generated by the PLL circuit of the digital signalprocessor 16 at an output timing of the track jump signal TJ to theservo circuit 14 and outputs it to the digital signal processor 16. Thedigital signal processor 16 can supply the stable clock signal CK evenin the case of a track jump by locking the oscillation band of the PLLcircuit in an output interval of the PLL hold signal.

FIG. 15 is a timing chart showing a characteristic operation of thephysical position information acquiring device 80 when the optical discof the second embodiment is a Blu-ray disc.

The digital reproduction signal DS outputted from the digital signalprocessor 16 of the physical position information acquiring device 80 tothe formatter 17 is formatted by the physical cluster as a unit forerror correction of main information corresponding to the concave andconvex mark by the formatter 17. One physical cluster is made up of 16address units having addresses. Further, one address unit can be dividedinto 31 frames with synchronization codes. Further, one frame is made upof 1932 channel bits and has a synchronization code of 30 channel bitsat the leading end.

The counter 35 of the physical position information acquiring device 80is a counter synchronized with the clock signal CK from the digitalsignal processor 16 and includes the channel bit counter for countingthe clock signal CK and the frame counter for counting the frame pulsesindicating the leading end positions of the frames from the formatter17.

The channel bit counter counts the number of clocks in synchronism withthe clock signal CK and is reset at the timing of the frame pulse FPLS.In other words, the channel bit counter operates as a counter forcounting 0 to 1931 per frame.

The frame counter is a counter for counting the frame pulses and counts0 to 15 per address unit. The frame counter is reset at an update timingof the address information ADR inputted from the formatter 17.

Next, a method for detecting the premark is described. The physicalposition information acquiring device 80 irradiates the laser lighthaving reproduction intensity to the concave and convex marks of theoptical disc and generates the analog reproduction signal AS from thereflected light. In the digital signal processor 16, the clock signal CKsynchronized with the analog reproduction signal AS is extracted fromthis analog reproduction signal AS by the internally provided PLLcircuit. The digital signal processor 16 also generates the digitalreproduction signal DS by quantizing this analog reproduction signal ASin synchronism with the clock signal CK and slicing the quantizedreproduction signal at a slice level SL1 to binarize the reproductionsignal.

The premark PM straight in the radial direction is so prerecorded in thecontrol region CTL at the inner circumferential side as to cross thetrack of the concave and convex marks MK. In the second embodiment, anoperation in the case of forming the premark by improving thereflectivity through the irradiation of laser light is described.

If the premark is present during the reproduction by tracking on theconcave and convex marks, the modulation factor of the analogreproduction signal AS is increased since the reflectivity is higherthan a maximum level H of the reflected light during the reproduction ofthe concave and convex marks.

The slicer 34 generates a premark detection signal PMDET by slicing thequantized reproduction signal RD at a slice level SL2 for detecting thepremark position of the level higher than the slice level SL1 forbinarizing the analog reproduction signal AS and higher than the maximumlevel H of the reflected light from the concave and convex marks, andoutputs it to the counter 35.

The counter 35 stops the counting operations of the channel bit counterand the frame counter provided inside upon detecting the rise of thepremark detection signal PMDET and holds the respective count values(channel bit count value BCNT and frame count value FCMT).

The held frame count value FCMT and channel bit count value BCNT aretransferred as the premark position information POS to the memory 11together with the address information ADR, and saved in the memory 11.

As described above, the physical position information acquiring device80 can extract the premark position information from the referenceaddress to the premark starting position based on the address of thereproduction signal, the frame position and the channel bit position. Bysetting the slice levels for binarizing the analog reproduction signalAS respectively for the concave and convex marks and the premark, it ispossible to detect the concave and convex marks and the premark whiledistinguishing them. Although the premark whose reflectivity isincreased by the irradiation of laser light is described in the secondembodiment, a level lower than the minimum level of the reflected lightfrom the concave and convex marks is conversely set as the slice levelSL2 for premark detection in the case of the premark in a non-reflectingstate by removing the reflective film.

If no large difference is confirmed between the maximum level of thereflected light from the concave and convex marks and the maximum levelof the reflected light from the premark, if no large difference isconfirmed between the minimum level of the reflected light from theconcave and convex marks and the minimum level of the reflected lightfrom the premark or if the reproduction signal cannot be normally sliceddue to large noise of the premark portion, the slice level SL1 for theconcave and convex marks may be set as the slice level SL2 for premarkdetection. In this case, the premark and the concave and convex markscan be distinguished by detecting that the output interval (=premarkwidth) of the premark detection signal is wider than the maximum widthof the concave and convex marks in the circumferential direction.

Next, an optical disc reproduction device according to the secondembodiment is described. FIG. 16 is a block diagram showing theconstruction of the optical disc reproduction device according to thesecond embodiment. An optical disc reproduction device 71 shown in FIG.16 is provided with a spindle motor 12, an optical head 13, a servocircuit 14, an analog signal processor 15, a digital signal processor16, a formatter 17, an error corrector 24, a timing generator 18, arandom number generator 19, a PE modulator 21, a LPF 25, a binarizer 26,a correlation integrator 27, a memory 11, an authentication codeverifier 29, an AD 33, a slicer 34, a counter 35 and a system controller23.

The optical disc reproduction device 71 according to the secondembodiment is a combination of the optical disc reproduction device 7shown in FIG. 8 and the physical position information acquiring device80 shown in FIG. 14. Since the respective constituent elements are thesame as those of the optical disc reproduction device 7 and the physicalposition information acquiring device 80, they are not described.

In this embodiment, the formatter 17, the memory 11, the authenticationcode verifier 29, the AD 33, the slicer 34 and the counter 35 correspondto an example of a position confirming unit, and the system controller23 to examples of a comparing unit and a reproduction limiting unit.

FIGS. 17 and 18 are flow charts showing an illegal disc judgment processin the optical disc reproduction device according to the secondembodiment. In the optical disc reproduction device 71, the illegal discjudgment process is started when the power supply is turned on and theoptical disc is inserted. A start timing may be set before an access tothe encrypted program or cyclically set at specified intervals.

First of all, an optical disc 241 is loaded into the optical discreproduction device 71 (Step S1). After completing the loading, thesystem controller 23 causes the optical head 13 to seek the position ofan address N (e.g. in a user area) where the physical positioninformation is recorded by the recordable mark formed by irradiatinglaser light in the track direction to change the reflectivity of thereflective film (Step S2).

After completing the seek, the system controller 23 reproduces thesub-information (physical position information) recorded on the opticaldisc (Step S3). Since the reproduction procedure of this physicalposition information is similar to that of the medium ID in the opticaldisc reproduction device 71 of the first embodiment, it is not describedhere.

Subsequently, the system controller 23 performs an error correction tothe physical position information based on parity for error correctionassigned to the reproduced physical position information by the errorcorrector 24 and judges whether or not the error correction was normallyperformed (Step S4). As a result, if the error correction is judged tobe impossible (NO in Step S4), this routine returns to Step S2 tocontinue the reproduction operation of the sub-information, assumingthat the integration time is short.

On the other hand, if the error correction is judged to have beennormally performed (YES in Step S4), the system controller 23 saves thesub-information (physical position information) in the memory 11 (StepS5).

The system controller 23 generates an alteration preventing code (hashvalue for verification) for verification anew from the physical positioninformation, and judges whether the generated alteration preventing codefor verification and the alteration preventing code (reproduced hashvalue) assigned to the physical position information match. In this way,the system controller 23 judges whether or not the physical positioninformation has been altered (Step S6). If the both alterationpreventing codes match, the system controller 23 continues the process,judging that there is no illegal alteration in the physical positioninformation. On the other hand, unless the both alteration preventingcodes match, the system controller 23 moves onto an operation ofinterrupting the process, judging that the physical position informationhas been altered or the optical disc is an optical disc manufactured byan illegal maker.

If the alteration is judged (YES in Step S6), this routine proceeds to areproduction stop processing in Step S15 and the subsequent Step. On theother hand, if no alteration is judged (NO in Step S6), the systemcontroller 23 obtains a reference address M used to detect the premarkposition information extracted at the time of recording from thephysical position information (Step S7). Subsequently, the systemcontroller 23 causes the optical head 13 to seek the obtained referenceaddress M (Step S8).

When the optical head 13 reaches the reference address M, the premarkdetection operation is started. Since the premark detection operation issimilar to the operation of the physical position information acquiringdevice 80 of the second embodiment, it is not described here. If thepremark detection operation for detecting the premark positioninformation is completed, the frame position information (frame countvalue FCNT) and the channel bit position information (channel bit countvalue BCNT) from the reference address M are outputted as describedabove (Step S9).

Subsequently, the system controller 23 compares the frame count valueFCNT included in the sub-information (physical position information)reproduced in Step S3 and the frame count value FCNT obtained in thepremark detection operation and judges whether or not the both framecount values FCNT match (Step S10). If the both frame count values FCNTare judged not to match (NO in Step S10), this routine proceeds to arewrite processing in Step S13 and subsequent Steps.

If the both frame count values FCNT are judged to match (YES in StepS10), the system controller 23 compares the channel bit count value BCNTincluded in the sub-information (physical position information)reproduced in Step S3 and the channel bit count value BCNT obtained inthe premark detection operation and judges whether or not the bothchannel bit count value BCNT match (Step S11). If the both channel bitcount values BCNT are judged not to match (NO in Step S11), this routineproceeds to the retry processing in Step S13 and subsequent Steps. Thisroutine proceeds to the next processing if the both count values matchwhile proceeding with the retry processing if they do not match (StepS11).

On the other hand, if the both channel bit count values BCNT are judgedto match (YES in Step S11), the system controller 23 judges whether ornot all the premarks have been detected (Step S12). Here, unless it isjudged that all the premarks have been detected (NO in Step S12), thisroutine proceeds to the processing in Step S8 and the system controller23 causes the optical head 13 to seek a reference address for confirmingthe position information of the next premark. If it is judged that allthe premarks have been detected (YES in Step S12), the system controller23 permits the reproduction operation and ends the illegal disc judgmentprocess.

Next, the retry processing in Step S13 and subsequent Steps isdescribed. If the both channel bit count values BCNT or the both framecount values FCNT are judged not to match in Steps S10 or S11, thesystem controller 23 increments a retry number saved beforehand (StepS13).

Subsequently, the system controller 23 judges whether or not the retrynumber as a result of increment lies in a permissible range (Step S14).If the retry number is judged to lie in the permissible range (YES inStep S14), the routine returns to the processing in Step S8 again andthe system controller 23 causes the optical head 13 to seek thereference address M to perform the premark detection operation. On theother hand, if the retry number is judged to exceed the permissiblerange (NO in Step S14), the reproduction stop processing in Step S15 andsubsequent Step follows.

Next, the reproduction stop processing in Step S15 and subsequent Stepis described. The reproduction stop processing is a processing forejecting the optical disc as an illegal disc when the retry numberexceeds the permissible range or when the alteration is judged to havebeen made. First of all, the system controller 23 stops the reproductionoperation currently in process (Step S15). At this time, it is desirablenot to receive any command except the one to eject the optical disc.

When the reproduction operation is stopped, the system controller 23generates and outputs error information. This error informationdesirably includes the cause having led to the stop of the reproductionoperation (Step S16). The error information is outputted to anddisplayed on a display device such as a monitor to be notified to theuser.

As described above, in the case of, for example, the alteration of thephysical position information recorded by the recordable mark, theoptical disc is judged to be an illegal disc and the reproductionoperation can be stopped by the illegal disc judgment process by theoptical disc reproduction device. Further, unless the premark positioninformation at the time of recording included in the physical positioninformation and the premark position information detected by the opticaldisc reproduction device match, the reproduction operation can bestopped, assuming the optical disc to be an illegally copied disc.Therefore, the reproduction of the optical disc recorded with theillegally altered physical position information or the optical discduplicated from a proper one can be stopped and the rights ofcopyrighted works recorded on the optical disc can be protected.

Further, the construction of the optical disc reproduction device 71 isrealized to include both the construction of the physical positioninformation acquiring device 80 in the third manufacturing process 600of the optical disc manufacturing method according to the secondembodiment and that of the optical disc reproduction device 7 accordingto the first embodiment. In other words, the optical disc reproductiondevice according to the second embodiment can be realized to have boththe function of detecting the physical position information of thepremark in the physical position information acquiring device 80 and thefunction of reproducing the sub-information in the optical discreproduction device 7 according to the first embodiment. A program forrealizing the above illegal disc judgment process is stored in theoptical disc reproduction device of the second embodiment.

Although the above illegal disc judgment process is described to detectthe premark position information at two points distanced by thespecified distance in the radial direction at the same reference addressfor the sake of simplifying the description, the position information oftwo points distanced from one reference address in the radial directionmay be detected to judge the linearity of the premark. Specifically, thepremark position is detected on the same track recorded with thereference address and the same address position is sought again aftermaking an inward movement to cross one track. When the target addressposition is reached again, the premark position is confirmed by movingthe track position several tracks toward the inner or outer side. Evenif the premark is illegally copied and not straight in the radialdirection, a jump of several tracks is made in the radial direction tojudge the presence or absence of the premark again after the presence orabsence of the premark is judged based on the reference address, wherebythe reproduction of the optical disc is stopped, judging that thepremark is not straight or there is no consistency in the physicalposition information.

Although the position information on all the premarks is conformed inthe illegal disc judgment process of the second embodiment, the presentinvention is not particularly limited to this. Only some of the recordedpremarks may be confirmed to shorten the reproduction starting time. Forexample, out of eight premarks radially formed, the position informationon only four premarks may be confirmed.

Third Embodiment (3-1) Optical Disc According to Third Embodiment

FIG. 19 is a conceptual diagram showing the construction of an opticaldisc according to a third embodiment. An optical disc 150 of the thirdembodiment includes a user region 151, on which content data isrecorded, and a sub-information recording region 152, on which theidentification information of the optical disc 150 is recorded.

Content data is recorded in the form of concave and convex marksbeforehand in the user region 151, and neither concave and convex marksnor wobble guide grooves are recorded in the sub-information recordingregion 152. A reflective film of the optical disc 150 is a recordingfilm whose reflectivity changes by the irradiation of laser light.

No special synchronization codes are included in the sub-informationrecording region 152 where the identification information of the opticaldisc 150 is recorded, and the identification information is recordedfrom the same angular position as that of the leading end position of anaddress unit 153 having an address as a reference of the user region151.

The angular position information of the optical disc is determined inaccordance with a rotation synchronization signal outputted from aspindle motor of an optical disc recording device or an optical discreproduction device. The optical disc recording device or the opticaldisc reproduction device generates a clock signal synchronized with onerotation by a PLL control of the rotation synchronization signalsynchronized with one rotation of the disc. The angular position of theoptical disc is calculated by a count value (FG Counter) of theseclocks.

In an example of FIG. 19, 360 counts are made for one rotation of thedisc. In other words, one cycle of clock is generated at every rotationangle of 1° of the disc and the counter synchronized with this countsone per clock to extract the angle information. In this example, theaddress unit as a reference of an address value M starts when the countvalue is “300”. Thus, the optical disc recording device moves an opticalhead to a radial position corresponding to the sub-information recordingregion after the leading end position of the address unit having theaddress value M is reproduced beforehand to extract the count value ofthe rotational synchronization, and records the identificationinformation bit by bit in synchronism with the clock of the rotationsynchronization signal from the count value of “300” of rotationalsynchronization.

In the above manner, in the optical disc 150 of the third embodiment,after the content data is recorded in the form of the concave and convexmarks in the user region 151 beforehand, the angle information of thereference address position in the user region 151 is extracted and theidentification information of the optical disc is additionally recordedfrom an extracted angle in the sub-information recording region 152.

The identification information can be used to record medium uniqueinformation. Since the identification information can be recorded on theoptical disc having the concave and convex marks transferred theretobeforehand, information unique to each optical disc can be additionallyrecorded even if the optical disc is a read-only optical discmanufactured by transferring concave and convex marks using a stamper.

Although 360 counts are made per one rotation, i.e. 1 count is made atevery rotation of 1° of the optical disc in the third embodiment, thepresent invention is not limited to this. Any resolution may be adoptedprovided that it can reliably discriminate the reference addressposition. For example, in the case of a Blu-ray disc, 32 address unitsare recorded per one rotation near a radial position of 23 mm.Accordingly, in this case, resolution is sufficient to be equal to orabove 63 counts (1 count at every rotation of 5.6°) per one rotation soas to be able to reliably discriminate 32 address positions.

(3-2) Optical Disc Recording Device According to Third Embodiment

Next, an optical disc recording device according to the third embodimentis described. FIG. 20 is a block diagram showing the construction of theoptical disc recording device according to the third embodiment. Theoptical disc recording device 250 shown in FIG. 20 is provided with aspindle motor 12, an optical head 13, a servo circuit 14, an analogsignal processor 15, a digital signal processor 16, a formatter 17, aPLL circuit 38, an angle meter 39, a random number generator 19, an EOR40, a memory 11, a laser intensity modulator 22 and a system controller23.

The spindle motor 12 rotates an optical disc when the optical disc isloaded into the optical disc recording device 250. The optical head 13irradiates the optical disc with laser light having reproductionintensity, generates a channel signal CS from the reflected light andoutputs it to the analog signal processor 15.

The analog signal processor 15 generates a focus error signal FEindicating a displacement of a focus position at a position where thelaser light of the optical head 13 is irradiated and a tracking errorsignal TE indicating a displacement in the radial direction between atrack position of the concave and convex marks and a position irradiatedwith the laser light from the channel signal CS inputted from theoptical head 13, and outputs them to the servo circuit 14. The analogsignal processor 15 also extracts signal components corresponding toconcave and convex marks in accordance with the channel signal CSinputted from the optical head 13, generates an analog reproductionsignal AS by amplifying or equalizing the waveforms of the extractedsignal components, and output it to the digital signal processor 16.

The servo circuit 14 generates a focus control signal FC for correctingthe displacement of the focus position from the focus error signal FEinputted from the analog signal processor 15 and a tracking controlsignal TC for correcting the displacement of the tracking position fromthe tracking error signal TE, and outputs them to the optical head 13.The servo circuit 14 also calculates a linear velocity at the radialposition, where the information is being reproduced, in accordance withthe channel signal CS, calculates a rotation speed from the reproductionsignal, generates a rotation control signal SC to attain an optimalrotation speed and outputs it to the spindle motor 12.

When the optical disc is loaded, the optical disc recording device 250first seeks a reference address position preset in the system controller23 and moves one track toward the inner circumferential side per onerotation, whereby the track position at the reference address positionis held and the rotation speed corresponding to the radial position ofthe reference address position is held.

The digital signal processor 16 extracts the clock signal CKsynchronized with the analog reproduction signal AS inputted from theanalog signal processor 15 by a PLL circuit provided inside, generates abinary digital reproduction signal DS by quantizing the inputted analogreproduction signal AS in synchronism with the clock signal CK andoutputs it to the formatter 17.

The formatter 17 detects synchronization codes assigned at specifiedtime intervals from the digital reproduction signal DS inputted from thedigital signal processor 16, reconfigures it by the frame at a detectiontiming, divides each frame by the address unit including addressinformation by a synchronization pattern of the synchronization codes,extracts address information ADR assigned to each address unit andoutput it to the angle meter 39.

The PLL circuit 38 is constructed by a general PLL circuit, calculates aphase error between the rotation synchronization signal FS inputted fromthe spindle motor 12 and the clock signal CK generated inside andchanges the frequency of the clock signal CK generated inside so thatthe phase error becomes “0”. Accordingly, in the PLL circuit 38, theclock signal CK synchronized with the rotation of the optical disc canbe generated and is outputted to the angle meter 39, the random numbergenerator 19 and the memory 11.

The angle meter 39 counts the clock signal CK from the PLL circuit 38 tomeasure the angular position of the optical disc. The angle meter 39counts the clock signal CK from the PLL circuit 38, and saves a countvalue at the timing of the leading end position of the address unithaving the reference address information if the address information ADRfrom the formatter 17 is reference address information preset in thesystem controller 23. In other words, the angle meter 39 extracts andholds the angular position of the reference address position.

If the angular position of the reference address position is measured bythe angle meter 39, the system controller 23 controls the spindle motor12 by a CAV control to make an angular velocity constant, and moves theoptical head 13 to a radial position corresponding to thesub-information recording region at the inner circumferential side ofthe disc.

After the optical head 13 is moved to the sub-information recordingregion, the PLL circuit 38 generates a clock signal CK synchronized withthe rotation synchronization signal FS from the spindle motor 12 andoutputs it to the angle meter 39 in a manner similar to the above.

The angle meter 39 counts the clock signal CK inputted from the PLLcircuit 38, generates a count value indicating the angular position ofthe saved reference address as angular position information ANG, andoutputs it to the random number generator 19 and the memory 11.

The memory 11 stores the sub-information (medium unique information) SDinputted beforehand, and outputs the sub-information SD bit by bit tothe EOR 40 in synchronism with the inputted clock signal CK inaccordance with the angular position information ANG from the anglemeter 39. The memory 11 outputs the sub-information bit by bit in a bitorder from a position “0” of the angular position information, i.e. fromthe angular position of the reference address.

The random number generator 19 is reset at the leading end position ofthe angular position information ANG inputted from the angle meter 39similar to the memory 11, generates a pseudo random sequence RN bit bybit in synchronism with the clock signal CK and outputs it to the EOR40. The random number generator 19 is a general M-sequence generatorincluding a shift register, and shifts the internal shift register insynchronism with the clock signal CK inputted from the PLL circuit 38 togenerate the pseudo random sequence RN bit by bit.

The EOR 40 is a general XOR gate, calculates an exclusive OR of thesub-information SD from the memory 11 and the pseudo random sequence RNfrom the random number generator 19 to generate recording data WD, andoutputs it to the laser intensity modulator 22.

The laser intensity modulator 22 generates a recording pulse WPindicating the timing and intensity of the irradiation of recordinglaser light in accordance with the recording data WD inputted from theEOR 40, and outputs it to the optical head 13.

The optical head 13 controls the value of a current flowing into a laserbased on the recording pulse WP inputted from the laser intensitymodulator 22 and irradiates laser light, thereby forming a recordablemark in the sub-information recording region of the optical disc torecord the sub-information (medium unique information).

In the above manner, the optical disc recording device 250 moves theoptical head 13 to the sub-information recording region aftercalculating the angular position of the reference address recorded inthe form of concave and convex marks beforehand by means of a counter inaccordance with the clock signal CK generated from the rotationsynchronization signal FS, and records the sub-information insynchronism with the clock signal synchronized with the rotationsynchronization signal FS from the same angular position as the angularposition information of the reference address. In this way, the mediumunique information and the like can be recorded even on an optical discmanufactured by the transfer by a stamper.

Further, the optical disc recording device 250 of the third embodimentrecords the sub-information scrambled with the pseudo random sequence RNby generating the pseudo random sequence RN based on the angularposition of the address recorded by the concave and convex marks. Thus,if the optical disc is illegally duplicated, there is an error betweenthe angular position of the reference address and that of the startingposition where the sub-information is recorded and the pseudo randomsequence RN cannot be generated at a correct timing. Therefore, thereproduction operation of such an illegal disc can be stopped.

In this embodiment, the PLL circuit 38 corresponds to an example of aclock generator, the angle meter 39 to an example of a reference angleextracting unit, the optical head 13, the random number generator 19,the EOR 40, the memory 11 and the laser intensity modulator 22 to anexample of a sub-information recording unit.

FIG. 21 is a timing chart showing a characteristic operation of theoptical disc recording device according to the third embodiment. Firstof all, when an optical disc is loaded into the optical disc recordingdevice 250, the optical disc is rotated by the spindle motor 12 and theoptical head 13 is moved to a position having a reference address (M).

Further, the PLL circuit 38 generates a clock signal CK synchronizedwith a rotation synchronization signal FS in accordance with therotation synchronization signal FS outputted from the spindle motor 12.

The optical head 13 irradiates the optical disc with laser light havingreproduction intensity, extracts a channel signal CS from the reflectedlight, and outputs it to the analog signal processor 15. The analogsignal processor 15 generates an analog reproduction signal AS inaccordance with the channel signal CS and outputs it to the digitalsignal processor 16. The digital signal processor 16 generates a digitalreproduction signal DS by quantizing and binarizing the analogreproduction signal AS. The formatter 17 detects synchronization codesassigned at specified time intervals from the digital reproductionsignal DS, formats the digital reproduction signal DS by the frame, anddivides each frame into address units having address information ADRbased on the synchronization pattern of the synchronization codes.

The angle meter 39 is a counter synchronized with the clock signal CKinputted from the PLL circuit 38, and extracts and saves a count valueof clocks corresponding to the leading end position of the address unitindicating the reference address if the address information ADR inputtedfrom the formatter 17 is the reference address preset in the systemcontroller 23. In this example, the reference address is “M” and thecount value corresponding to the leading end position of the addressunit of the reference address is “300”.

After the measurement of the count value (angular position) of thereference address position is completed, the rotation of the spindlemotor 12 is controlled through the CAV control to move the optical head13 to the radial position corresponding to the sub-information recordingregion at the inner circumferential side of the optical disc. Even afterthe optical head 13 reaches the sub-information recording region, theangle meter 39 similarly counts the clock signal CK synchronized withthe rotation synchronization signal FS.

The memory 11 outputs the sub-information saved inside beforehand bit bybit in synchronism with the clock signal CK from the position where thecount value is the count value of the reference address saved in theangle meter 39. In other words, the memory 11 outputs thesub-information bit by bit from the same angular position as thereference address.

The random number generator 19 similarly outputs the pseudo randomsequence RN bit by bit from the same angular position as the referenceaddress. The EOR 40 calculates an exclusive OR of the sub-information SDfrom the memory 11 and the pseudo random sequence RN from the randomnumber generator 19 to generate recording data WD scrambled with thesub-information.

The laser intensity modulator 22 generates a recording pulse WPindicating a timing of irradiating recording laser light and a recordingpower based on the recording data WD inputted from the EOR 40. Theoptical head 13 irradiates the optical disc with the laser light basedon the recording pulse WP to form recordable marks, whose reflectivitywas changed, on the disc surface, whereby the sub-information isadditionally recorded.

As described above, if the optical disc recording device 250 is used,medium unique information unique to each optical disc can be recorded inthe sub-information recording region with the same angular position asthe reference address of the concave and convex marks as a startingpoint after the optical disc is produced even if the optical disc is aread-only optical disc having concave and convex marks transferredthereto.

The reference address position and the starting point of recording themedium unique information are displaced due to a displacement betweenthe recording starting points of an optical disc at a copy source and anoptical disc at a copy destination or due to a deviation of linearvelocity or rotation speed. If such a displacement occurs, the startingpoint of reproducing the medium unique information is displaced andcorrect information cannot be reproduced. Therefore, the reproduction ofan illegally duplicated optical disc can be prohibited.

(3-3) Optical Disc Reproduction Device According to Third Embodiment

Next, an optical disc reproduction device according to the thirdembodiment is described. FIG. 22 is a block diagram showing theconstruction of an optical disc reproduction device 350 according to thethird embodiment. The optical disc reproduction device 350 shown in FIG.22 is provided with a spindle motor 12, an optical head 13, a servocircuit 14, an analog signal processor 15, a digital signal processor16, a formatter 17, a PLL circuit 38, an angle meter 39, a random numbergenerator 19, an AD 41, a binarizer 42, an EOR 43, a memory 11 and asystem controller 23.

The spindle motor 12 rotates an optical disc when the optical disc isloaded into the optical disc reproduction device 350. The optical head13 irradiates the optical disc with reproduction laser light, generatesa channel signal CS from the reflected light and outputs it to theanalog signal processor 15.

The analog signal processor 15 generates a focus error signal FEindicating a displacement of a focus position of the laser light and atracking error signal TE indicating a displacement of a radial positionof the laser light with respect to the track position of the concave andconvex marks from the channel signal CS inputted from the optical head13, and outputs them to the servo circuit 14. The analog signalprocessor 15 also extracts signal components of the channel signal CScorresponding to the concave and convex marks, generates an analogreproduction signal AS by amplifying or equalizing the waveforms of theextracted signal components, and output it to the digital signalprocessor 16.

The servo circuit 14 generates a focus control signal FC for correctingthe displacement of the focus position from the focus error signal FEinputted from the analog signal processor 15 and a tracking controlsignal TC for correcting the displacement of the tracking position fromthe tracking error signal TE, and outputs them to the optical head 13.The servo circuit 14 also calculates a linear velocity at the radialposition, where the information is being reproduced, in accordance withthe channel signal CS, generates a rotation control signal SC forcorrecting the rotation speed by judging a deviation from the currentlinear velocity, and outputs it to the spindle motor 12.

The digital signal processor 16 extracts the clock signal CKsynchronized with the analog reproduction signal AS inputted from theanalog signal processor 15 by a PLL circuit provided inside, generates adigital reproduction signal DS by quantizing and binarizing the inputtedanalog reproduction signal AS in synchronism with the clock signal CKand outputs it to the formatter 17.

The formatter 17 detects synchronization codes assigned at specifiedtime intervals to the digital reproduction signal DS inputted from thedigital signal processor 16, formats the digital reproduction signal DSby the frame, divides each frame into address units including addressinformation by a synchronization pattern of the synchronization codes,extracts address information ADR assigned to each address unit andoutput it to the angle meter 39.

The PLL circuit 38 is constructed by a general PLL circuit, calculates aphase error between the rotation synchronization signal FS inputted fromthe spindle motor 12 and the clock signal CK generated inside andcontrols the frequency of the clock signal CK so that the phase errorbecomes “0”. Accordingly, the PLL circuit 38 generates the clock signalCK synchronized with the rotation synchronization signal FS, and outputsit to the AD 41, the angle meter 39 and the random number generator 19.

The angle meter 39 includes a counter for counting the clock signal CKinputted from the PLL circuit 38, extracts and saves the count value ofthe counter at the leading end position of the address unit of areference address when the reference address preset in the systemcontroller 23 and the address information ADR inputted from theformatter 17 are equal. In other words, since the counter counts theclock signal CK synchronized with the rotation synchronization signalFS, it measures the angular position of the optical disc. To extract thecount value at the leading end position of the address unit indicated bythe reference address means to extract the angular position at theleading end position of the address unit indicated by the referenceaddress.

After the angular position of the reference address is extracted by theangle meter 39, the system controller 23 controls the spindle motor 12by a CAV control to make an angular velocity constant, and moves theoptical head 13 to a radial position corresponding to thesub-information recording region at the inner circumferential side ofthe disc.

After the optical head 13 is moved to the sub-information recordingregion, the PLL circuit 38 generates a clock signal CK synchronized withthe rotation synchronization signal FS from the spindle motor 12 andoutputs it to the angle meter 39 in a manner similar to the above. Theangle meter 39 counts the clock signal CK inputted from the PLL circuit38 and outputs the count value as angular position information ANG tothe random number generator 19.

The random number generator 19 generates a pseudo random sequence RN bitby bit in synchronism with the clock signal CK using the current angularposition as a starting point if the count value of the reference addresssaved in the angle meter 39 and the current count value is equal, i.e.if the angular position at the reference address position and thecurrent angular position are equal, and outputs it to the EOR 40.

The AD 41 is constructed by a general analog-to-digital converter,generates a quantized reproduction signal DAS by sampling and quantizingthe analog reproduction signal AS from the analog signal processor 15 insynchronism with the clock signal CK from the PLL circuit 38, andoutputs it to the binarizer 42.

The binarizer 42 generates a binary reproduction signal BS by binarizingthe quantized reproduction signal DAS inputted from the AD 41 andoutputs it to the EOR 43. Since the optical disc reproduction device 350executes no tracking control to the recordable marks at the time ofreproducing the sub-information recording region, the reproductionsignal of the sub-information recording region can be divided intoreflected light free from the recordable marks and reflected lightcrossing or scanning the recordable marks. The binarizer 42 outputs adifference between these two reflected lights after binarizing it. Thus,if the quantized reproduction signal DAS is binarized after beingaveraged in a specified band using a low-pass filter, it can be moreefficiently binarized.

The EOR 43 is constructed by a general XOR gate and calculates anexclusive OR of the binary reproduction signal BS from the binarizer 42and the pseudo random sequence RN from the random number generator 19.Since the random number generator 19 is constructed similar to that ofthe optical disc recording device 250 according to the third embodiment,the sub-information SD scrambled with the pseudo random sequence RN atthe time of recording is descrambled by the EOR 403. Thus, the EOR 43generates descrambled sub-information SD and outputs it to the memory11. The memory 11 saves the descrambled sub-information SD bit by bit.

As described above, the optical disc reproduction device 350 extractsthe angular position of the leading end position of the address unitindicated by the reference address and reproduces the sub-informationfrom the sub-information recording region of the optical disc using theextracted angular position as a recording starting point. On anillegally duplicated optical disc, a reference address position and arecording starting point of sub-information are displaced due to adisplacement of the recording starting point or a deviation of linearvelocity or rotation speed. Thus, it is impossible to reproduce thesub-information at the correct starting point and correctsub-information cannot be reproduced from the illegally duplicatedoptical disc.

The optical disc reproduction device 350 stops the reproductionoperation upon judging that no correct sub-information is beingreproduced. A method for judging as to the correct sub-information issuch that the sub-information is recorded as an error correction code atthe time of recording, an error correction is performed after thereproduction of the sub-information, and the reproduction operation isstopped assuming that no correct sub-information can be reproduced whencorrection impossibility or an error is detected. Alternatively, analteration preventing code such as a MAC is assigned at the time ofrecording the sub-information, the MAC is calculated from thesub-information detected at the time of reproduction, it is confirmedwhether or not the calculated MAC and the MAC assigned to thesub-information match, and the reproduction operation is stoppedassuming that no correct sub-information is recorded unless the two MACsmatch.

In this embodiment, the PLL circuit 38 corresponds to an example of aclock generator, the angle meter 39 to an example of a reference angleextracting unit, the random number generator 19, the AD 41, thebinarizer 42, the EOR 43 and the memory 11 to an example of asub-information reproducing unit.

FIG. 23 is a timing chart showing a characteristic operation of theoptical disc reproduction device according to the third embodiment. ThePLL circuit 38 generates a clock signal CK synchronized with a rotationsynchronization signal FS from the spindle motor 12.

The optical head 13 irradiates the optical disc with reproduction laserlight, generates a channel signal CS from the reflected light andoutputs it to the analog signal processor 15. The analog signalprocessor 15 generates an analog reproduction signal AS in accordancewith the channel signal CS and outputs it to the digital signalprocessor 16. The PLL circuit of the digital signal processor 16extracts the clock signal CK synchronized with the analog reproductionsignal AS and generates a digital reproduction signal DS by quantizingand binarizing the analog reproduction signal AS.

The formatter 17 detects synchronization codes assigned at specifiedtime intervals from the digital reproduction signal DS inputted from thedigital signal processor 16, formats the digital reproduction signal DSby the frame, and divides each frame into address units includingaddress information ADR in accordance with the synchronization patternof the synchronization codes.

The angle meter 39 counts the clock signal CK synchronized with therotation of the optical disc from the PLL circuit 38 and measures therotational position (angular position) of the optical disc. The anglemeter 39 also saves the count value at the leading end position of theaddress unit indicated by the reference address preset in the systemcontroller 23, i.e. the angular position of the reference address. Inthis example, the reference address is “M” and the angular position ofthe reference address is “300”.

After the measurement of the angular position of the reference addressis completed, the rotation of the spindle motor 12 is controlled throughthe CAV control to make the angular velocity constant, and moves theoptical head 13 to a radial position corresponding to thesub-information recording region at the inner circumferential side ofthe optical disc.

Since no tracking control is executed to the recordable marks SMK in thesub-information recording region, the optical disc is irradiated withthe laser light having reproduction intensity and the analogreproduction signal AS is generated from the reflected light. Further,the analog reproduction signal AS is binarized by the binarizer 42 anddivided into areas where the recordable marks SMK are absent and areaswhere the recordable marks SMK are present.

Similarly in the reproduction of the sub-information recording region,the PLL circuit 38 generates a clock signal CK synchronized with therotation of the optical disc, and the angle meter 39 counts the clocksignal CK to calculate the angular position of the optical disc.

The random number generator 19 generates the pseudo random sequence RNbit by bit in synchronism with the clock signal CK from the same angularposition as the reference address based on the count value of the anglemeter 39. The EOR 43 reproduces the sub-information SD by descramblingthe binary reproduction signal BS to be reproduced by the pseudo randomsequence RN generated by the random number generator 19.

As described above, the optical disc reproduction device 350 extractsthe angular position of the leading end position of the address unitindicated by the reference address position beforehand, and reproducesthe sub-information from the sub-information recording region of theoptical disc using the extracted angular position as a starting point.On an illegally duplicated optical disc, a reference address positionand a recording starting point of sub-information are displaced due to adisplacement of the recording starting point or a deviation of linearvelocity or rotation speed. Thus, it is impossible to reproduce thesub-information at the correct starting point and correctsub-information cannot be reproduced from the illegally duplicatedoptical disc.

The optical disc reproduction device 350 stops the reproductionoperation upon judging that no correct sub-information is beingreproduced. A method for judging as to the correct sub-information issuch that the sub-information is recorded as an error correction code atthe time of recording, an error correction is performed after thereproduction of the sub-information, and the reproduction operation isstopped assuming that no correct sub-information can be reproduced whencorrection impossibility or an error is detected. Alternatively, analteration preventing code such as a MAC is assigned at the time ofrecording the sub-information, the MAC is calculated from thesub-information detected at the time of reproduction, it is confirmedwhether or not the calculated MAC and the MAC assigned to thesub-information match, and the reproduction operation is stoppedassuming that no correct sub-information is recorded unless the two MACsmatch.

According to the optical disc, the optical disc recording device and theoptical disc reproduction device of this embodiment, the angularposition of the reference address out of the addresses indicated by thetransferred concave and convex marks is reproduced and thesub-information is recorded in the sub-information recording regionusing the angular position of the reference address as the startingpoint.

Similarly, the angular position of the reference address similar to theone at the time of recording and indicated by the transferred concaveand convex marks can be calculated and the sub-information can bereproduced from the sub-information recording region using the angularposition of the reference address as a starting point.

Specifically, whether or not the angular position of the referenceaddress of the concave and convex marks at the time of recording and theone at the time of reproduction match can be judged by the reproductionoperation of the sub-information. Normally, if an optical disc isillegally duplicated, the angular position of the reference address andthat of the sub-information recorded position are displaced due to adisplacement of the recorded position or an error of linear velocity orrotation speed. If these relationships deviate, it is impossible toreproduce the sub-information since a correct timing of reproducing thesub-information cannot be generated. Therefore, the reproduction of anillegal optical disc can be prohibited.

A recordable mark non-recording region where no recordable mark SMK isto be recorded may be set on the optical disc according to the thirdembodiment based on the count value of the angle meter 39 upon recordingthe sub-information in the sub-information recording region. By doingso, a so-called mirror region where neither the recordable marks SMK northe concave and convex marks MK are recorded is formed as a fan-shapedregion in a part of the sub-information recording region. This mirrorregion is desirably wider than a tracking servo pursuit zone wheretracking is performed. By doing so, even if it is tried to duplicate therecordable marks SMK by performing a tracking control to the recordablemarks SMK, it is impossible to perform the tracking control in therecordable mark non-recording region and, hence, duplicate therecordable marks SMK.

Although the reference address for extracting the angular position isthe fixed value preset in the system controller 23 in the thirdembodiment, it is not limited to this. For example, an arbitrary addressis selected at the time of recording and is recorded as the referenceaddress instead of the medium ID described in the first embodiment.Since the sub-information is recorded based on the address positiondifferent for each optical disc in this way, the illegal analysis of theoptical disc can be prevented. In this case, the address is desirablyrecorded while having an alteration preventing code assigned thereto orbeing encrypted. In this way, it is virtually impossible for a piratemarker having no legal encryption key to record the address information.

Since no tracking control is performed to the recordable marks SMK inthe reproduction from the sub-information recording region, thesub-information is desirably recorded in a range of a plurality oftracks in the radial direction of the optical disc.

Of course, the sub-information may be read by performing tracking to therecordable marks SMK. In this case, the recordable marks SMK arereproduced by providing no recordable mark non-recording region at allor by performing no tracking control in the recordable marknon-recording region. The recordable mark non-recording region may berecorded by irradiating the laser light to the reflective film on thetracks of the concave and convex marks MK to change the reflectivitylike the medium ID of the first embodiment. In this case, it is possibleto set the recordable mark non-recording region unique to each medium.

In the third embodiment, 360 counts are made per one rotation by theangle meter 39. The sub-information is extracted by judging whether ornot the recordable mark is present in each of 360 blocks obtained bydividing the optical disc in the circumferential direction. Thus, byforming recordable marks SMK or scratch blocks through the removal ofthe reflective film in arbitrary ones of these blocks, the medium ID ofthe first embodiment may, for example, be recorded depending on in whichblocks the recordable mark SMK or the scratch block is present.

Although the sub-information is reproduced by one rotation of thesub-information recording region in the third embodiment, thereproduction mode is not limited to this. Normally, if the recordablemarks SMK are reproduced without any tracking control, there is apossibility of reproducing mirror regions between the recordable marksin a partial region. Thus, the correct sub-information cannot bereproduced at this time. Accordingly, the stable sub-information can bereproduced if the reproduced binary reproduction signals BS areintegrated and extracted in synchronism with a one-rotation timing whilea movement is made toward the inner or outer circumferential side in theradial direction during one rotation.

Further, if the sub-information recording region is divided into aplurality of areas according to the radial positions and differentreference addresses or different random sequences are set for therespective areas, security strength can be improved.

Similarly, if different pieces of information are recorded in aplurality of areas according to the radial positions, the recordingcapacity of the sub-information can be increased.

Although no concave and convex marks MK are formed in thesub-information recording region in the third embodiment, the presentinvention is not limited to this. Even if the recordable marks SMK arerecorded on the concave and convex marks MK, the recording band of theconcave and convex marks MK is sufficiently higher than the recordablemark band. Thus, the concave and convex marks MK and the recordablemarks SMK can be easily separated, wherefore the recordable marks SMKcan be stably reproduced.

(4) OTHER EMBODIMENTS

Here, another recording mode of the recordable marks is describedalthough it is not described in the first and second embodiments. Themedium ID is recorded by the recordable marks in the first embodiment,and the physical position information is recorded by the recordablemarks in the second embodiment. FIGS. 24 are diagrams showing recordingmodes of recordable marks according to other embodiments.

In the first and second embodiments, the shape and formation positionsof the recordable marks can be variously changed. FIG. 24A is a diagramshowing recordable marks intermittently formed between tracks, FIG. 24Bis a diagram showing a recordable mark formed in a meandering manner onconcave and convex marks, FIG. 24C is a diagram showing recordable markshaving a short interval in a circumferential direction andintermittently formed, FIG. 24D is a diagram showing a recordable marklonger than the length of the concave and convex marks in a radialdirection and continuously formed, and FIG. 24E is a diagram showingrecordable marks longer than the length of the concave and convex marksin the radial direction and intermittently formed.

In FIG. 24A, the recordable marks SMK are intermittently formed betweenthe tracks of the concave and convex marks MK in a band lower than thelongest one of the concave and convex marks in the circumferentialdirection. Although one recordable mark SMK is recorded in the bandlower than the longest one of the concave and convex marks in thecircumferential direction in the first embodiment, the influence on thereproduction accuracy of the concave and convex marks MK can be furtherreduced if recordable marks are intermittently formed. A positionbetween the tracks does not necessarily means the center between thetracks of the concave and convex marks. Upon performing tracking betweenthe tracks of the concave and convex marks MK, the recordable marks MKare formed at positions displaced from the central position between thetracks by offsetting the track position beforehand. Thus, the detectionaccuracy of the recordable marks SMK can be improved since therecordable marks SMK are detected by performing tracking to the tracksof the concave and convex marks MK at the time of reproduction.

In FIG. 24B, the recordable mark SMK is formed on the concave and convexmarks MK in a meandering manner. Although the recordable mark SMK isformed straight in the circumferential direction in the firstembodiment, the present invention is not particularly limited to thisand the recordable mark SMK may be formed in a meandering manner in thecircumferential direction.

In FIG. 24C, the recordable marks SMK are formed to have nonuniformwidth in the radial direction. Such recordable marks SMK are formed byincreasing or decreasing the laser intensity upon being recorded torecord a plurality of recording pulses (multipulse) and to narrow themultipulse width of each pulse, i.e. to shorten the irradiation time ofthe laser light having recording intensity. The recordable marks SMK areintermittent, but close to each other in the circumferential direction,wherefore the recordable marks SMK are connected.

In FIG. 24D, the recordable mark SMK is formed longer than the concaveand convex marks MK in the radial direction. Depending on thecharacteristic of the recordable mark SMK, cases are known where themodulation factor of the concave and convex marks MK is higher at thetime of reproduction even if the recordable mark SMK thicker than theconcave and convex marks MK in the radial direction is formed at thetime of recording. Thus, in such cases, the recordable mark SMK thickerthan the concave and convex marks MK in the radial direction may beformed.

In FIG. 24E, the recordable marks SMK are intermittently formed to belonger than the concave and convex marks in the radial direction similarto FIG. 24D. In this case, the influence on the reproduction accuracy ofthe concave and convex marks MK can be reduced since the recordablemarks SMK are intermittently formed.

Any mode shown in FIGS. 24A to 24E lies in the scope of the presentinvention and obtains the same effects as those in the respectiveembodiments. The present invention is not limited to such shapes. Allthe inventions of recording the recordable marks by changing thereflectivity of the disc after the production of the disc by recordingthe concave and convex marks lie in the scope of the present invention.

Although the medium ID is recorded by the recordable marks in the firstembodiment and the physical position information is recorded by therecordable marks in the second embodiment, the present invention is notlimited to this. For example, any information on digital copyrightedworks to be recorded such as information on decryption including keyinformation for decrypting encrypted contents recorded in the userregion, certificate data indicating that the optical disc is legitimate,information on the number of times, time and period the content is movedor permitted to duplicate and information indicating an illegal disc canbe recorded.

The above specific embodiments mainly embrace inventions having thefollowing constructions.

An optical disc according to one aspect of the present invention is anoptical disc in which a reflective film is formed on concave and convexmarks after the concave and convex marks synchronized with the integralmultiple of a channel bit length are formed in accordance with modulatedmain information and which is characterized in that, after the opticaldisc is produced, continuous or intermittent laser light synchronizedwith the integral multiple of the channel bit length is irradiated atintervals longer than the longest one of the concave and convex marks inaccordance with a spiral track formed in the circumferential directionof the concave and convex marks to change an optical characteristic ofthe reflective film, thereby forming a recordable mark to recordsub-information necessary to reproduce the main information in asuperimposition manner.

According to this construction, after the reflective film is formed onthe concave and convex marks of the optical disc, the continuous orintermittent laser light synchronized with the integral multiple of thechannel bit length is irradiated at intervals longer than the longestone of the concave and convex marks in accordance with the spiral trackformed in the circumferential direction of the concave and convex marks.Thus, the recordable mark is formed by changing the opticalcharacteristic of the reflective film, and the sub-information necessaryto reproduce the main information is recorded in a superimpositionmanner.

Thus, the sub-information necessary to reproduce the main informationcan be recorded in a superimposition manner without deteriorating thereading accuracy of the main information, so that the illegalduplication of the optical disc can be prevented.

In the above optical disc, the width of the recordable mark in a radialdirection is preferably narrower than that of the concave and convexmarks in the radial direction. According to this construction, since thewidth of the recordable mark in the radial direction is narrower thanthat of the concave and convex marks in the radial direction, thefluctuation of the reflected light level caused by forming therecordable mark at the time of reproduction can be made smaller than themodulation factor of the concave and convex marks and the deteriorationin the reproduction accuracy of the concave and convex marks can bereduced.

In the optical disc, the recordable mark is preferably formed on thespiral track formed in the circumferential direction of the concave andconvex marks. According to this construction, the recordable mark can beformed on the spiral track formed in the circumferential direction ofthe concave and convex marks.

In the above optical disc, the recordable mark is preferably formedbetween track parts of the spiral track formed in the circumferentialdirection of the concave and convex marks. According to thisconstruction, the recordable mark can be formed between the track partsof the spiral track formed in the circumferential direction of theconcave and convex marks. Since the recordable mark is formed betweenthe track parts adjacent in the radial direction, the recordable markcan be formed without influencing the reproduction accuracy of theconcave and convex marks. Since the recordable mark is formed bychanging the reflectivity between the track parts of the concave andconvex marks, there is no influence on the reproduction of the concaveand convex marks as the main information and, in addition, the trackpitches of the concave and convex marks are the same regardless of thepresence or absence of the recordable mark. Therefore, there is nolikelihood of reducing the disc capacity.

In the above optical disc, the recordable mark is preferably formed atan intermediate position between a first track having the concave andconvex marks and a second track adjacent to the first track. Accordingto this construction, since the recordable mark is formed at theintermediate position between the first track having the concave andconvex marks and the second track adjacent to the first track, therecordable mark can be formed without influencing the reproductionaccuracy of the concave and convex marks. It should be noted that theintermediate position means not only a central part between the firstand second tracks, but also a substantially central part between thefirst and second tracks.

In the above optical disc, the recordable mark is preferably formedcloser to the first track than the intermediate position between thefirst track having the concave and convex marks and the second trackadjacent to the first track. According to this construction, therecordable mark can be formed closer to the first track than theintermediate position between the first track having the concave andconvex marks and the second track adjacent to the first track.

In the above optical disc, 1 bit of the sub-information is preferablyrecorded with a plurality of recordable marks. According to thisconstruction, 1 bit of the sub-information can be recorded with theplurality of recordable marks.

In the above optical disc, 1 bit of the sub-information is preferablyrecorded as a set of recordable marks intermittently formed. Accordingto this construction, 1 bit of the sub-information can be recorded as aset of the intermittently formed recordable marks.

In the above optical disc, the length of the recordable mark in thecircumferential direction is preferably equal to or shorter than ashortest mark length of the concave and convex marks in thecircumferential direction. According to this construction, therecordable mark can be formed without deteriorating the reproductionaccuracy of the concave and convex marks since the length of therecordable mark in the circumferential direction is equal to or shorterthan the shortest mark length of the concave and convex marks in thecircumferential direction.

In the above optical disc, the length of the recordable mark in thecircumferential direction is preferably equal to or shorter than thechannel bit length. According to this construction, the recordable markcan be formed without deteriorating the reproduction accuracy of theconcave and convex marks since the length of the recordable mark in thecircumferential direction is equal to or shorter than the channel bitlength.

In the above optical disc, a modulation factor of the recordable mark asa fluctuation of the reflected light level caused by forming therecordable mark is preferably smaller than a modulation factor of theconcave and convex marks as a difference between the reflected lightlevel of the concave and convex marks and that of the reflective filmother than the concave and convex marks.

According to this construction, the modulation factor of the recordablemark as the fluctuation of the reflected light level caused by formingthe recordable mark is smaller than that of the concave and convex marksas the difference between the reflected light level of the concave andconvex marks and that of the reflective film other than the concave andconvex marks. Thus, the concave and convex marks can be reproduced whilethe influence by the recordable mark is suppressed.

In the above optical disc, the modulation factor of the recordable markis preferably averagely smaller than half that of the concave and convexmarks. According to this construction, since the modulation factor ofthe recordable mark is averagely smaller than half that of the concaveand convex marks, there is no likelihood of erroneously reproducing anedge position of a reproduction signal of the concave and convex marks.Thus, the recordable mark can be formed without influencing reproductionaccuracy of the concave and convex marks.

In the above optical disc, the recordable mark is preferably formed byincreasing the reflectivity of the reflective film in a part irradiatedwith the laser light. According to this construction, the recordablemark is formed by increasing the reflectivity of the reflective film inthe part irradiated with the laser light. Since the reflectivity of ametal film of a read-only optical disc normally decreases upon theirradiation of the laser light, the sub-information cannot be recordedunless the reflectivity of the reflective film in the part irradiatedwith the laser light is increased in the optical disc. Therefore, theillegal duplication of the optical disc can be prevented.

In the above optical disc, the sub-information is recorded while beingfrequency diffused by a pseudo random sequence. According to thisconstruction, since the sub-information is recorded while beingfrequency diffused by the pseudo random sequence, it is difficult todistinguish from noise components even if it is tried to apply frequencyanalysis to the fluctuation of the reflectivity. Therefore, it can beprevented to illegally duplicate an optical disc by analyzing thesub-information.

In the above optical disc, the sub-information is preferably recorded byapplying a PE modulation. According to this construction, since thesub-information is recorded by applying the PE modulation, an occurrenceprobability is substantially equal in a part where the reflectivity ischanged and in a part where the reflectivity is not changed. It can beavoided to apply direct-current components to a tracking signal and areproduction signal at the time of reproduction.

In the above optical disc, it is preferable that the recordable mark isformed in a direction orthogonal to the track on the concave and convexmarks, and that the sub-information includes physical positioninformation indicating a physical position of a region, where therecordable mark is formed, on the optical disc.

According to this construction, the recordable mark is formed in thedirection orthogonal to the track on the concave and convex marks, andthe sub-information includes the physical position informationindicating the physical position of the region, where the recordablemark is formed, on the optical disc. Thus, at the time of reproduction,whether or not the optical disc is an illegally duplicated optical disccan be judged by detecting a physical position of the recordable markformed in the direction orthogonal to the track on the concave andconvex marks and comparing the detected position with the physicalposition information recorded beforehand, whereby the reproduction ofthe illegally duplicated optical disc can be prohibited.

An optical disc manufacturing method according to another aspect of thepresent invention comprises a mastering step of producing an opticaldisc master formed with concave and convex marks synchronized with theintegral multiple of a channel bit length in accordance with modulatedmain information; a stamping step of transferring the concave and convexmarks of the optical disc master to an optical disc substrate; asputtering step of forming a reflective film on the optical discsubstrate; and a sub-information recording step of irradiatingcontinuous or intermittent laser light synchronized with the integralmultiple of the channel bit length at intervals longer than the longestone of the concave and convex marks in accordance with a spiral trackformed in a circumferential direction of the concave and convex marks tochange an optical characteristic of the reflective film after thereflective film is formed on the concave and convex marks of the opticaldisc in the sputtering step, thereby forming a recordable mark to recordsub-information necessary to reproduce the main information in asuperimposition manner.

According to this construction, in the mastering step, the optical discmaster formed with the concave and convex marks synchronized with theintegral multiple of the channel bit length is produced in accordancewith the modulated main information. The concave and convex marks of theoptical disc master are transferred to the optical disc substrate in thestamping step, and the reflective film is formed on the optical discsubstrate in the sputtering step. After the reflective film is formed onthe concave and convex marks of the optical disc in the sputtering step,the continuous or intermittent laser light synchronized with theintegral multiple of the channel bit length is irradiated at theinterval longer than the longest one of the concave and convex marks inaccordance with the spiral track formed in the circumferential directionof the concave and convex marks in the sub-information recording step,whereby the optical characteristic of the reflective film is changed toform the recordable mark and the sub-information necessary to reproducethe main information is recorded in a superimposition manner.

Accordingly, the sub-information necessary to reproduce the maininformation can be recorded without deteriorating the reading accuracyof the main information, so that the illegal duplication of the opticaldisc can be prevented.

An optical disc recording device according to still another aspect ofthe present invention is an optical disc recording device for recordingsub-information necessary to reproduce main information on an opticaldisc prerecorded with the main information by concave and convex marksin a superimposition manner, comprising a tracking unit for controllinga position to be irradiated with laser light in accordance with a spiraltrack formed in a circumferential direction of the concave and convexmarks; a reproduction signal extracting unit for extracting areproduction signal from the reflected light of reproduction laser lightirradiated to the concave and convex marks; a clock extracting unit forextracting a channel clock synchronized with a channel bit length of theconcave and convex marks; and a sub-information recording unit forirradiating recording laser light synchronized with a band which is theintegral multiple of the channel clock and lower than the band of thereproduction signal to change an optical characteristic of a reflectivefilm formed on a recording surface of the optical disc, thereby forminga recordable mark to record the sub-information on the optical disc in asuperimposition manner.

According to this construction, the position to be irradiated with thelaser light in accordance with the spiral track formed in thecircumferential direction of the concave and convex marks prerecordedwith the main information is controlled by the tracking unit. Thereproduction signal is extracted from the reflected light of thereproduction laser light irradiated to the concave and convex marks bythe reproduction signal extracting unit, and the channel clocksynchronized with the channel bit length of the concave and convex marksis extracted by the clock extracting unit. Subsequently, the recordinglaser light synchronized with the band which is the integral multiple ofthe channel clock and lower than the band of the reproduction signal isirradiated and the optical characteristic of the reflective film formedon the recording surface of the optical disc is changed to form therecordable mark by the sub-information recording unit, whereby thesub-information necessary to reproduce the main information is recordedon the optical disc in a superimposition manner.

Accordingly, the sub-information necessary to reproduce the maininformation can be recorded without deteriorating the reading accuracyof the main information, so that the illegal duplication of the opticaldisc can be prevented.

An optical disc reproduction device according to further another aspectof the present invention is an optical disc reproduction device forreproducing main information from concave and convex marks of an opticaldisc and reproducing sub-information necessary to reproduce the maininformation from a recordable mark formed by changing an opticalcharacteristic of a reflective film of the optical disc through theirradiation of laser light, comprising a tracking unit for controlling aposition to be irradiated with the laser light in accordance with aspiral track formed in a circumferential direction of the concave andconvex marks; a reproduction signal extracting unit for extracting areproduction signal from the reflected light of reproduction laser lightirradiated to the concave and convex marks; a clock extracting unit forextracting a channel clock synchronized with a channel bit length fromthe reproduction signal; a separating unit for separating a concave andconvex mark reproduction signal corresponding to the concave and convexmarks and a recordable mark reproduction signal corresponding to therecordable mark from the reproduction signal; and a sub-informationreproducing unit for reproducing the sub-information from the recordablemark reproduction signal synchronized with a band which is the integralmultiple of the channel clock and lower than the band of the concave andconvex mark reproduction signal.

According to this construction, the position to be irradiated with thelaser light in accordance with the spiral track formed in thecircumferential direction of the concave and convex marks pre-recordedwith the main information is controlled by the tracking unit. Thereproduction signal is extracted from the reflected light of thereproduction laser light irradiated to the concave and convex marks thereproduction signal extracting unit, and the channel clock synchronizedwith the channel bit length is extracted from the reproduction signal bythe clock extracting unit. Subsequently, the concave and convex markreproduction signal corresponding to the concave and convex marks andthe recordable mark reproduction signal corresponding to the recordablemark are separated from the reproduction signal by the separating unit,and the sub-information necessary to reproduce the main information isreproduced from the recordable mark reproduction signal synchronizedwith the band which is the integral multiple of the channel clock andlower than the band of the concave and convex mark reproduction signalby the sub-information reproducing unit.

Accordingly, the sub-information necessary to reproduce the maininformation can be reproduced without deteriorating the reading accuracyof the main information, so that the illegal duplication of the opticaldisc can be prevented.

In the above optical disc reproduction device, it is preferable that asynchronization code detector for detecting synchronization codesassigned at specified intervals from the reproduction signal is furtherprovided; and that the sub-information reproducing unit reproduces thesub-information in synchronism with detection timings of thesynchronization codes by the synchronization code detector.

According to this construction, the synchronization codes assigned atthe specified intervals are detected from the reproduction signal by thesynchronization code detector, and the sub-information is reproduced insynchronism with the detection timings of the synchronization codes bythe synchronization code detector by the sub-information reproducingunit. Since the synchronization codes are assigned to the reproductionsignal at the specified intervals beforehand and the sub-information isreproduced in synchronism with the detection timings of thesesynchronization codes, the sub-information can be easily reproduced.

In the above optical disc reproduction device, the sub-informationreproducing unit preferably includes a correlation sequence generatorfor generating a correlation sequence, a correlation detector fordetecting a correlation value of the correlation sequence generated bythe correlation sequence generator and the recordable mark reproductionsignal, and a reproducer for reproducing the sub-information based onthe correlation value detected by the correlation detector.

According to this construction, the correlation sequence is generated bythe correlation sequence generator, the correlation value of thecorrelation sequence generated by the correlation sequence generator andthe recordable mark reproduction signal is detected by the correlationdetector and the sub-information is reproduced based on the correlationvalue detected by the correlation detector by the reproducer. Thus, thesub-information can be reproduced based on the correlation value of thegenerated correlation sequence and the recordable mark reproductionsignal.

In the above optical disc reproduction device, it is preferable that asynchronization code detector for detecting synchronization codesassigned at specified intervals from the reproduction signal is furtherprovided; and that the correlation sequence generator generates thecorrelation sequence in synchronism with detection timings of thesynchronization codes detected by the synchronization code detector.

According to this construction, the synchronization codes assigned atthe specified intervals are detected from the reproduction signal by thesynchronization code detector and the correlation sequence is generatedin synchronism with the detection timings of the synchronization codesdetected by the synchronization code detector by the correlationsequence generator. Since the synchronization codes are assigned to thereproduction signal at the specified intervals beforehand and thecorrelation sequence is generated in synchronism with the detectiontimings of these synchronization codes, the sub-information can bereproduced based on the correlation value of the correlation sequencegenerated in synchronism with the detection timings of thesynchronization codes and the recordable mark reproduction signal.

In the above optical disc reproduction device, the separating unitpreferably includes a band-limiting filter for extracting signalcomponents in a band lower than a band corresponding to the concave andconvex marks as the recordable mark reproduction signal from thereproduction signal.

According to this construction, the signal components in the band lowerthan the band corresponding to the concave and convex marks areextracted as the recordable mark reproduction signal from thereproduction signal by the band-limiting filter. Thus, the concave andconvex mark reproduction signal and the recordable mark reproductionsignal can be separated by the band-limiting filter, whereforeaccuracies in reproducing the both reproduction signals can be ensured.

In the above optical disc reproduction device, it is preferable that therecordable mark is formed in a direction orthogonal to the track on theconcave and convex marks; the sub-information includes physical positioninformation indicating a physical position of a region, where therecordable mark is formed, on the optical disc; and that the opticaldisc reproduction device further comprises a position confirming unitfor confirming the physical position information of the recordable markformed orthogonally to the track with respect to a concave and convexmark position, a comparing unit for comparing the physical positioninformation included in the sub-information reproduced by thesub-information reproducing unit and the physical position informationconfirmed by the position confirming unit and a reproduction limitingunit for limiting the reproduction of the main information if the piecesof physical position information do not match as a result of thecomparison by the comparing unit.

According to this construction, the recordable mark is formed in thedirection orthogonal to the track on the concave and convex marks, andthe sub-information includes the physical position informationindicating the physical position of the region, where the recordablemark is formed, on the optical disc. The physical position informationof the recordable mark formed orthogonally to the track with respect tothe concave and convex mark position is confirmed by the positionconfirming unit, and the physical position information included in thesub-information reproduced by the sub-information reproducing unit andthe physical position information confirmed by the position confirmingunit are compared by the comparing unit. Thereafter, if the pieces ofphysical position information do not match as a result of comparison bythe comparing unit, the reproduction of the main information is limitedby the reproduction limiting unit.

Accordingly, in the case of an illegally duplicated disc, there is nocorrelation between the physical position information at the time ofrecording and the physical position information at the time ofreproduction and these pieces of physical position information do notmatch. Thus, the reproduction of the main information is limited and thereproduction of information from the illegally duplicated optical disccan be prevented.

An optical disc according to another aspect of the present invention isan optical disc including a main information recording region where maininformation is recorded by concave and convex marks and asub-information recording region where sub-information necessary toreproduce the main information is recorded by a recordable mark formedby irradiating laser light after the concave and convex marks areformed, wherein the recordable mark is formed in the sub-informationrecording region by irradiating the laser light from a recordingstarting point based on an angular position of a reference position inthe main information recording region to change the reflectivity of areflective film, whereby the sub-information is recorded in asuperimposition manner.

According to this construction, the optical disc includes the maininformation recording region where the main information is recorded bythe concave and convex marks and the sub-information recording regionwhere the sub-information necessary to reproduce the main information isrecorded by the recordable mark formed by irradiating the laser lightafter the concave and convex marks are formed. The recordable mark isformed in the sub-information recording region by irradiating the laserlight from the recording starting point based on the angular position ofthe reference position in the main information recording region tochange the reflectivity of the reflective film, whereby thesub-information is recorded in a superimposition manner.

Accordingly, there is a displacement between a reference position and arecording starting point for sub-information due to a displacement ofthe recording starting point or a deviation of linear velocity orrotation speed on an illegally duplicated optical disc, wherefore thesub-information cannot be reproduced from a correct recording startingpoint. Hence, the correct sub-information cannot be reproduced from theillegally duplicated optical disc and the reproduction of the maininformation from the illegally duplicated optical disc can be prevented.

In the above optical disc, the sub-information recording regionpreferably includes a recordable mark non-recording region, where therecordable mark is not formed, in a specified angle range of thesub-information recording region. According to this construction, sincethe sub-information recording region includes the recordable marknon-recording region, where the recordable mark is not formed, in thespecified angle range, a tracking control is impossible in therecordable mark non-recording region even if it is tried to duplicatethe recordable mark by executing the tracking control to the recordablemark. Thus, it is impossible to duplicate the recordable mark and theillegal duplication of the optical disc can be prevented.

In the above optical disc, information specifying the reference positionis preferably recorded by irradiating laser light onto the spiral trackin the circumferential direction of the concave and convex marks tochange the reflectivity of the reflective film.

According to this construction, since the information specifying thereference position is preferably recorded by irradiating the laser lightonto the spiral track in the circumferential direction of the concaveand convex marks to change the reflectivity of the reflective film, anarbitrary reference position is, for example, selected at the time ofrecording and the selected reference position is recorded by changingthe reflectivity of the reflective film. Thus, a different referenceposition is recorded for each optical disc, wherefore the illegalanalysis of the optical disc can be prevented.

An optical disc recording device according to another aspect of thepresent invention is an optical disc recording device for recording maininformation and sub-information on an optical disc including a maininformation recording region where main information is recorded byconcave and convex marks and a sub-information recording region wheresub-information necessary to reproduce the main information is recordedby a recordable mark formed by irradiating laser light after the concaveand convex marks are formed, the optical disc recording devicecomprising a clock generator for generating a clock signal synchronizedwith the rotation of the optical disc; a reference angle extracting unitfor extracting an angular position of a reference position in the maininformation recording region; and a sub-information recording unit forirradiating laser light synchronized with the clock signal generated bythe clock generator from a recording starting point in thesub-information recording region specified based on the angular positionextracted by the reference angle extracting unit to record thesub-information in a superimposition manner.

According to this construction, the optical disc includes the maininformation recording region where the main information is recorded bythe concave and convex marks and the sub-information recording regionwhere the sub-information necessary to reproduce the main information isrecorded by the recordable mark formed by irradiating the laser lightafter the concave and convex marks are formed. The clock signalsynchronized with the rotation of the disc is generated by the clockgenerator, and the angular position of the reference position in themain information recording region is extracted by the reference angleextracting unit. Subsequently, the laser light synchronized with theclock signal generated by the clock generator is irradiated from therecording starting point in the sub-information recording regionspecified based on the angular position extracted by the reference angleextracting unit by the sub-information recording unit to record thesub-information in a superimposition manner.

Accordingly, there is a displacement between a reference position and arecording starting point for sub-information due to a displacement ofthe recording starting point or a deviation of linear velocity orrotation speed on an illegally duplicated optical disc, wherefore thesub-information cannot be reproduced from a correct recording startingpoint. Hence, the correct sub-information cannot be reproduced from theillegally duplicated optical disc and the reproduction of the maininformation from the illegally duplicated optical disc can be prevented.

In the above optical disc recording device, the reference position ispreferably specified by an address recorded by the concave and convexmarks. According to this construction, the reference position in themain information recording region can be specified by the addressrecorded by the concave and convex marks.

In the above optical disc recording device, the cycle of the clocksignal is preferably shorter than a cycle of recording the address.According to this construction, one or more recordable marks can berecorded in an address cycle since the cycle of the clock signal isshorter than the cycle of recording the address.

An optical disc reproduction device according to another aspect of thepresent invention is an optical disc reproduction device for reproducingmain information and sub-information from an optical disc including amain information recording region where main information is recorded byconcave and convex marks and a sub-information recording region wheresub-information necessary to reproduce the main information is recordedby a recordable mark formed by irradiating laser light after the concaveand convex marks are formed, the optical disc reproduction devicecomprising a clock generator for generating a clock signal synchronizedwith the rotation of the optical disc; a reference angle extracting unitfor extracting an angular position of a reference position in the maininformation recording region; and a sub-information reproducing unit forreproducing the sub-information in synchronism with the clock signalgenerated by the clock generator from a reproduction starting point inthe sub-information recording region specified based on the angularposition extracted by the reference angle extracting unit.

According to this construction, the optical disc includes the maininformation recording region where the main information is recorded bythe concave and convex marks and the sub-information recording regionwhere the sub-information necessary to reproduce the main information isrecorded by the recordable mark formed by irradiating laser light afterthe concave and convex marks are formed. The clock signal synchronizedwith the rotation of the disc is generated by the clock generator, andthe angular position of the reference position in the main informationrecording region is extracted by the reference angle extracting unit.Subsequently, the sub-information is reproduced in synchronism with theclock signal generated by the clock generator from the reproductionstarting point in the sub-information recording region specified basedon the angular position extracted by the reference angle extractingunit.

Accordingly, there is a displacement between a reference position and arecording starting point for sub-information due to a displacement ofthe recording starting point or a deviation of linear velocity orrotation speed on an illegally duplicated optical disc, wherefore thesub-information cannot be reproduced from a correct recording startingpoint. Hence, the correct sub-information cannot be reproduced from theillegally duplicated optical disc and the reproduction of the maininformation from the illegally duplicated optical disc can be prevented.

In the above optical disc reproduction device, the reference position ispreferably specified by an address recorded by the concave and convexmarks. According to this construction, the reference position in themain information recording region can be specified by the addressrecorded by the concave and convex marks.

In the above optical disc reproduction device, the cycle of the clocksignal is preferably shorter than a cycle of recording the address.According to this construction, one or more recordable marks can berecorded in an address cycle since the cycle of the clock signal isshorter than the cycle of recording the address.

INDUSTRIAL APPLICABILITY

The optical disc, the optical disc manufacturing method, the opticaldisc recording device and the optical disc reproduction device accordingto the present invention can not only record sub-information, but alsoprevent the illegal duplication on other optical discs even if theoptical disc is a read-only optical disc. Thus, there can be provided anoptical disc, an optical disc manufacturing method, an optical discrecording device and an optical disc reproduction device which hinderthe illegal infringement of the copyright of main information recordedon the optical disc.

1. An optical disc, comprising: concave and convex marks synchronizedwith the integral multiple of a channel bit length in accordance withmodulated main information and a reflective film formed on the concaveand convex marks after the concave and convex marks are formed; whereinafter the optical disc is produced, continuous or intermittent laserlight synchronized with the integral multiple of the channel bit lengthis irradiated at intervals longer than the longest one of the concaveand convex marks in accordance with a spiral track formed in thecircumferential direction of the concave and convex marks to change anoptical characteristic of the reflective film, thereby forming arecordable mark to record sub-information necessary to reproduce themain information in a superimposition manner. 2-10. (canceled)
 11. Anoptical disc according to claim 1, wherein the width of the recordablemark in a radial direction is narrower than that of the concave andconvex marks in the radial direction.
 12. An optical disc according toclaim 1, wherein the recordable mark is formed on the spiral trackformed in the circumferential direction of the concave and convex marks.13. An optical disc according to claim 1, wherein the recordable mark isformed between track parts of the spiral track formed in thecircumferential direction of the concave and convex marks.
 14. Anoptical disc according to claim 13, wherein the recordable mark isformed at an intermediate position between a first track having theconcave and convex marks and a second track adjacent to the first track.15. An optical disc according to claim 13, wherein the recordable markis formed closer to the first track than the intermediate positionbetween the first track having the concave and convex marks and thesecond track adjacent to the first track.
 16. An optical disc accordingto claim 1, wherein 1 bit of the sub-information is recorded with aplurality of recordable marks.
 17. An optical disc according to claim 1,wherein 1 bit of the sub-information is recorded as a set of therecordable marks intermittently formed.
 18. An optical disc according toclaim 17, wherein the length of the recordable mark in thecircumferential direction is equal to or shorter than a shortest marklength of the concave and convex marks in the circumferential direction.19. An optical disc according to claim 17, wherein the length of therecordable mark in the circumferential direction is equal to or shorterthan the channel bit length.
 20. An optical disc according to claim 1,wherein a modulation factor of the recordable mark as a fluctuation ofthe reflected light level caused by forming the recordable mark issmaller than a modulation factor of the concave and convex marks as adifference between the reflected light level of the concave and convexmarks and that of the reflective film other than the concave and convexmarks.
 21. An optical disc according to claim 20, wherein the modulationfactor of the recordable mark is averagely smaller than half that of theconcave and convex marks.
 22. An optical disc according to claim 1,wherein the recordable mark is formed by increasing the reflectivity ofthe reflective film in a part irradiated with the laser light.
 23. Anoptical disc according to claim 1, wherein the sub-information isrecorded while being frequency diffused by a pseudo random sequence. 24.An optical disc according to claim 1, wherein the sub-information isrecorded by applying a PE modulation.
 25. An optical disc according toclaim 1, wherein the recordable mark is formed in a direction orthogonalto the track on the concave and convex marks, and the sub-informationincludes physical position information indicating a physical position ofa region, where the recordable mark is formed, on the optical disc. 26.An optical disc manufacturing method, comprising: a mastering step ofproducing an optical disc master formed with concave and convex markssynchronized with the integral multiple of a channel bit length inaccordance with modulated main information; a stamping step oftransferring the concave and convex marks of the optical disc master toan optical disc substrate; a sputtering step of forming a reflectivefilm on the optical disc substrate; and a sub-information recording stepof irradiating continuous or intermittent laser light synchronized withthe integral multiple of the channel bit length at intervals longer thanthe longest one of the concave and convex marks in accordance with aspiral track formed in a circumferential direction of the concave andconvex marks to change an optical characteristic of the reflective filmafter the reflective film is formed on the concave and convex marks ofthe optical disc in the sputtering step, thereby forming a recordablemark to record sub-information necessary to reproduce the maininformation in a superimposition manner.
 27. An optical disc recordingdevice for recording sub-information necessary to reproduce maininformation on an optical disc prerecorded with the main information byconcave and convex marks, comprising: a tracking unit for controlling aposition to be irradiated with laser light in accordance with a spiraltrack formed in a circumferential direction of the concave and convexmarks; a reproduction signal extracting unit for extracting areproduction signal from the reflected light of reproduction laser lightirradiated to the concave and convex marks; a clock extracting unit forextracting a channel clock synchronized with a channel bit length of theconcave and convex marks; and a sub-information recording unit forirradiating recording laser light synchronized with a band which is theintegral multiple of the channel clock and lower than the band of thereproduction signal to change an optical characteristic of a reflectivefilm formed on a recording surface of the optical disc, thereby forminga recordable mark to record the sub-information on the optical disc in asuperimposition manner.
 28. An optical disc reproduction device forreproducing main information from concave and convex marks of an opticaldisc and reproducing sub-information necessary to reproduce the maininformation from a recordable mark formed by changing an opticalcharacteristic of a reflective film of the optical disc through theirradiation of laser light, comprising: a tracking unit for controllinga position to be irradiated with the laser light in accordance with aspiral track formed in a circumferential direction of the concave andconvex marks; a reproduction signal extracting unit for extracting areproduction signal from the reflected light of reproduction laser lightirradiated to the concave and convex marks; a clock extracting unit forextracting a channel clock synchronized with a channel bit length fromthe reproduction signal; a separating unit for separating a concave andconvex mark reproduction signal corresponding to the concave and convexmarks and a recordable mark reproduction signal corresponding to therecordable mark from the reproduction signal; and a sub-informationreproducing unit for reproducing the sub-information from the recordablemark reproduction signal synchronized with a band which is the integralmultiple of the channel clock and lower than the band of the concave andconvex mark reproduction signal. 29-33. (canceled)
 34. An optical discreproduction device according to claim 28, further comprising asynchronization code detector for detecting synchronization codesassigned at specified intervals from the reproduction signal, whereinthe sub-information reproducing unit reproduces the sub-information insynchronism with detection timings of the synchronization codes by thesynchronization code detector.
 35. An optical disc reproduction deviceaccording to claim 28, wherein the sub-information reproducing unitincludes: a correlation sequence generator for generating a correlationsequence, a correlation detector for detecting a correlation value ofthe correlation sequence generated by the correlation sequence generatorand the recordable mark reproduction signal, and a reproducer forreproducing the sub-information based on the correlation value detectedby the correlation detector.
 36. An optical disc reproduction deviceaccording to claim 35, further comprising a synchronization codedetector for detecting synchronization codes assigned at specifiedintervals from the reproduction signal, wherein the correlation sequencegenerator generates the correlation sequence in synchronism withdetection timings of the synchronization codes detected by thesynchronization code detector.
 37. An optical disc reproduction deviceaccording to claim 28, wherein the separating unit includes aband-limiting filter for extracting signal components in a band lowerthan a band corresponding to the concave and convex marks as therecordable mark reproduction signal from the reproduction signal.
 38. Anoptical disc reproduction device according to claim 28, wherein: therecordable mark is formed in a direction orthogonal to the track on theconcave and convex marks; the sub-information includes physical positioninformation indicating a physical position of a region, where therecordable mark is formed, on the optical disc; and the optical discreproduction device further comprises: a position confirming unit forconfirming the physical position information of the recordable markformed orthogonally to the track with respect to a concave and convexmark position, a comparing unit for comparing the physical positioninformation included in the sub-information reproduced by thesub-information reproducing unit and the physical position informationconfirmed by the position confirming unit; and a reproduction limitingunit for limiting the reproduction of the main information if the piecesof physical position information do not match as a result of thecomparison by the comparing unit.
 39. An optical disc, comprising:including a main information recording region where main information isrecorded by concave and convex marks and a sub-information recordingregion where sub-information necessary to reproduce the main informationis recorded by a recordable mark formed by irradiating laser light afterthe concave and convex marks are formed; wherein the recordable mark isformed in the sub-information recording region by irradiating the laserlight from a recording starting point based on an angular position of areference position in the main information recording region to changethe reflectivity of a reflective film, whereby the sub-information isrecorded in a superimposition manner.
 40. An optical disc according toclaim 39, wherein the sub-information recording region includes arecordable mark non-recording region, where the recordable mark is notformed, in a specified angle range of the sub-information recordingregion.
 41. An optical disc according to claim 39, wherein informationspecifying the reference position is recorded by irradiating laser lightonto the spiral track in the circumferential direction of the concaveand convex marks to change the reflectivity of the reflective film. 42.An optical disc recording device for recording main information andsub-information on an optical disc including a main informationrecording region where main information is recorded by concave andconvex marks and a sub-information recording region wheresub-information necessary to reproduce the main information is recordedby a recordable mark formed by irradiating laser light after the concaveand convex marks are formed, comprising: a clock generator forgenerating a clock signal synchronized with the rotation of the opticaldisc; a reference angle extracting unit for extracting an angularposition of a reference position in the main information recordingregion; and a sub-information recording unit for irradiating laser lightsynchronized with the clock signal generated by the clock generator froma recording starting point in the sub-information recording regionspecified based on the angular position extracted by the reference angleextracting unit to record the sub-information in a superimpositionmanner.
 43. An optical disc recording device according to claim 42,wherein the reference position is specified by an address recorded bythe concave and convex marks.
 44. An optical disc reproduction devicefor reproducing main information and sub-information from an opticaldisc including a main information recording region where maininformation is recorded by concave and convex marks and asub-information recording region where sub-information necessary toreproduce the main information is recorded by a recordable mark formedby irradiating laser light after the concave and convex marks areformed, comprising: a clock generator for generating a clock signalsynchronized with the rotation of the optical disc; a reference angleextracting unit for extracting an angular position of a referenceposition in the main information recording region; and a sub-informationreproducing unit for reproducing the sub-information in synchronism withthe clock signal generated by the clock generator from a reproductionstarting point in the sub-information recording region specified basedon the angular position extracted by the reference angle extractingunit.
 45. An optical disc reproduction device according to claim 44,wherein the reference position is specified by an address recorded bythe concave and convex marks.